qid int64 2 112k | question stringlengths 61 6.7k | positives listlengths 1 1 | negatives listlengths 1 10 |
|---|---|---|---|
8,586 | <p>If antibodies are produced against other blood groups' red blood cells, why can't antibodies form against white blood cells, of any blood group? (even the same one, as MHC will be different in almost all individuals)</p>
| [
{
"answer_id": 8589,
"pm_score": 4,
"text": "<p>Antibodies and other immune responses do indeed occur against the donor's white blood cells. However, white blood cells are present in relatively tiny quantities (<a href=\"https://www.mayoclinic.com/health/complete-blood-count/MY00476/DSECTION=results\">3... | [
{
"answer_id": 39059,
"pm_score": 1,
"text": "<p>Adding - very late to this - the most common symptom of a WBC incompatibility in a transfusion is a short-lived rash (looks like \"heat rash\") and low fever.</p>\n\n<p>The HLA antigens are not very \"antigenic\" compared to the main blood group antigens,... |
8,640 | <p>My understanding of evolution is that genetic mutation occurs in individual members of a species, and they become a new species.</p>
<p>Isn't a definition of species a group of genetically similar organisms that are pretty much exclusive in breeding ability?</p>
<p>Wouldn't there have to be a male and female with the same genetic divergence at the same time to make a new species? What is the popularly accepted mechanism for the splitting into a new species in organisms that require sexual reproduction?</p>
| [
{
"answer_id": 8644,
"pm_score": 3,
"text": "<blockquote>\n <p>My understanding of evolution is that genetic mutation occurs in individual members of a species, and they become a new species.</p>\n \n <p>Isn't a definition of species a group of genetically similar organisms that are pretty much exclu... | [
{
"answer_id": 8666,
"pm_score": 2,
"text": "<p>It should also be added that <a href=\"https://en.wikipedia.org/wiki/Allopatric_speciation\" rel=\"nofollow\">allopatric speciation</a> is arguably the most common form of speciation (compared to <a href=\"https://en.wikipedia.org/wiki/Sympatric_speciation... |
8,659 | <p>One lab I was in was paranoid about keeping it in a foil-wrapped conical tube; my current lab leaves it out on the bench (and it works fine for staining gels). It's the same company/concentration in both cases, but this second lab uses it up much faster.</p>
| [
{
"answer_id": 8662,
"pm_score": 3,
"text": "<p>Good question.</p>\n\n<p>I found this reference in \"<a href=\"http://books.google.com/books?id=PND76ZPTuXUC&pg=PA85&lpg=PA85&dq=ethidium%20bromide%20photobleaching&source=bl&ots=rz8SAHMknF&sig=m-kJFB5HJ1GNBIffBZYvLG1NTWU&hl=en&... | [
{
"answer_id": 8696,
"pm_score": 1,
"text": "<p>In my current lab we just leave the bottle out (but use it up pretty quickly as we have 20+ people). But we do buy 5 bottles at a time and leave them in the same spot as the bottle that is in use (inside a hood, with the light always turned on) and we've n... |
8,667 | <p>This is for a short story idea.</p>
<p>Is it possible to modify the DNA of a child to make their metabolism more susceptible (physical response, addiction, etc) to a certain type of chemical i.e. a chemical present in a fictional food. The idea being that their DNA is modified when in the womb (or before) and when they grow older (think teenager) they become addicted to said product.</p>
<p>This could be before conception, during pregnancy or after birth. What ways, in the future, could we go about doing this? Maybe chemical mutagens (<a href="http://en.wikipedia.org/wiki/Mutagen" rel="nofollow">http://en.wikipedia.org/wiki/Mutagen</a>) or site-directed mutagenesis (<a href="http://en.wikipedia.org/wiki/Site-directed_mutagenesis" rel="nofollow">http://en.wikipedia.org/wiki/Site-directed_mutagenesis</a>)? Gene therapy?</p>
<p>Or is there a way to alter the regulation of the physiological processes in the human body to make someone become easily addicted to a particular product?</p>
<p>I'm looking to have this aspect of the story as scientifically accurate as possible so I can examine the ethical questions around it within the story.</p>
| [
{
"answer_id": 8678,
"pm_score": 2,
"text": "<p>To extend with a theoretical way such a method might be possible (though I really hope this will never work or be done!) This is essentially a gene-therapy approach.</p>\n\n<ol>\n<li><p>Are you talking about psychological addiction (needing it to avoid run... | [
{
"answer_id": 8674,
"pm_score": 3,
"text": "<p>As fiction this is a reasonable premise, but at this point you are talking about what is called Gene Therapy - intentionally modifying or adding the sequence of a functional gene to change a deficiency of the subject. </p>\n\n<p>Gene therapy is a persisten... |
8,684 | <p>I always wonder about the capability of diversity of our antibodies. Do we have enough antibodies to fit to every kind of molecule? Wont't it be easier if our antibodies are like clay and can be molded to any form by antigens? Why to waste energy producing so many types of antibodies? </p>
<p>If some pathogen makes its antigens just like antibodies of our body, (I think) they won't ever be detected. So what would our body do?</p>
| [
{
"answer_id": 8691,
"pm_score": 4,
"text": "<p>As my answer is quite big I've highlighted the different regions I answer your question.</p>\n\n<h2>Intro and basic info</h2>\n\n<p>I take it you know how antibodies are made, but as a quick recap they're made by VDJ recombination of a limited but still qu... | [
{
"answer_id": 8686,
"pm_score": 2,
"text": "<p>The structure of a protein is largely dependent on what it is supposed to do. There is a little bit of wiggle room, but essentially, major changes in structure will also change the function of the protein.</p>\n\n<p>This is why it would be difficult (thoug... |
8,724 | <p>The volume of blood coursing the blood circulation is approximately five litres. A typical vein will stretch about eight times as much as corresponding artery. Because veins have high capacitance, large changes in blood volume have little effect on arterial blood pressure.
If the volume rise or falls, the elastic walls stretch or recoil, changing the volume of blood thus blood pressure in the nervous system.</p>
<p><strong>What else tissues can we consider?</strong>
I am interested in blood circulation and blood pressures in different tissues.</p>
| [
{
"answer_id": 8786,
"pm_score": 2,
"text": "<p>I'm not sure I understand your question very well-maybe try and rephrase it? As another example, low blood pressure in the kidneys is sensed by the juxtaglomerular apparatus which secretes renin into the circulation. Renin converts angiotensinogen (release... | [
{
"answer_id": 8965,
"pm_score": 0,
"text": "<p>The diameter of the blood vessel affects the speed of the flow of blood. Blood flow slows down as it moves from arteries to arterioles and subsequently to the capillaries because the cross-sectional area in the capillary beds is much bigger than the arteri... |
8,743 | <p>I have noticed that some TF binding sites are located in the introns of the genes.</p>
<p>I am puzzled about whether the TF only binds to DNA in the initiation stage of transcription and will detach during transcription. (I am thinking if the TF bind to the sense strand, it will block the PoLII for transcription, thus they should be removed.)</p>
<p>Many thanks in advance.</p>
| [
{
"answer_id": 8786,
"pm_score": 2,
"text": "<p>I'm not sure I understand your question very well-maybe try and rephrase it? As another example, low blood pressure in the kidneys is sensed by the juxtaglomerular apparatus which secretes renin into the circulation. Renin converts angiotensinogen (release... | [
{
"answer_id": 8965,
"pm_score": 0,
"text": "<p>The diameter of the blood vessel affects the speed of the flow of blood. Blood flow slows down as it moves from arteries to arterioles and subsequently to the capillaries because the cross-sectional area in the capillary beds is much bigger than the arteri... |
8,766 | <p>I'm looking at services like 23andme, and see that they identify a wide variety of genetic-based risks, like predisposition to diseases, hair loss, cancer, etc.</p>
<p><strong>Are there a more "positive" DNA analysis outcomes out there?</strong> Like increased strength, cheerfulness(resistance to depression), etc?</p>
| [
{
"answer_id": 8779,
"pm_score": 3,
"text": "<p>First of all, I think it is, to a large extent, the way you perceive it. Instead of cancer-causing allele and hair-loss allele, you can think of them as cancer-protection and great-hair alleles. If you don't have disease alleles, that means that in some se... | [
{
"answer_id": 8780,
"pm_score": 1,
"text": "<p>Lactase persistence is a recent mutation which enables the people who have it to drink and digest milk as adults, while the default state has people unable to digest milk after childhood.</p>\n\n<p>There is also a loci for muscle performance. People either... |
8,769 | <p>Are there good texts to study the evolution, how it works, and how mutations and changes lead to evolution of the organism ? </p>
<p>And how does the information increase through the long time using mutations and other mechanisms?</p>
<p>Can you recommend specific texts? </p>
| [
{
"answer_id": 8779,
"pm_score": 3,
"text": "<p>First of all, I think it is, to a large extent, the way you perceive it. Instead of cancer-causing allele and hair-loss allele, you can think of them as cancer-protection and great-hair alleles. If you don't have disease alleles, that means that in some se... | [
{
"answer_id": 8780,
"pm_score": 1,
"text": "<p>Lactase persistence is a recent mutation which enables the people who have it to drink and digest milk as adults, while the default state has people unable to digest milk after childhood.</p>\n\n<p>There is also a loci for muscle performance. People either... |
8,798 | <p>It is reasonably well known that many species, such as bees and some types of birds as examples can see into the ultraviolet (UV). How is the structure of their eye different to humans to allow this?</p>
<p>Also, how are they shielded from some of the harmful effects of ocular UV exposure?</p>
| [
{
"answer_id": 8820,
"pm_score": 3,
"text": "<p>Firstly most UV perceiving organisms only perceive far UV (~300-400nm) which is less damaging. There are different <a href=\"http://en.wikipedia.org/wiki/Photopsin\" rel=\"nofollow noreferrer\">opsins</a>, which get activated by different wavelengths. Like... | [
{
"answer_id": 76067,
"pm_score": -1,
"text": "<p>The relevant structure of the eye only differs in one way, the types of cones present, different types of cones contain different opsins (light sensitive pigments). Reptiles and birds have 4 cone types, Mammals have 2 (primates have 3). Early mammals <a... |
8,816 | <p>I'm looking at this <a href="http://www.ted.com/talks/manal_al_sharif_a_saudi_woman_who_dared_to_drive.html" rel="nofollow">Ted talk about a Saudi Arabia woman who dared to drive a car in the last few years</a>. This reminds me that until the last century or so, women (all over the world?) enjoyed less rights and might've been pigeonholed into roles predetermined by society. Those roles might've encouraged certain traits, and discouraged others. Those who did not conform might've been punished, like the woman in the talk above received death threats and was jailed.</p>
<p>This sounds to me like selective pressure, did it really exist, and did it have any effect on the genetics/traits of modern women?</p>
<p>This makes me interested in the question - <strong>compared to other species, are men and women more genetically different because of selective pressure put on women to conform to male-dominated world</strong> for thousands of years before 19th century?</p>
| [
{
"answer_id": 8827,
"pm_score": 4,
"text": "<p>I'm not sure I buy your premise: firstly, the degree and form of male-female differentiation in social roles has varied widely across time and culture in human history so I doubt it forms a uniform evolutionary driver such as you describe. Secondly, the de... | [
{
"answer_id": 8822,
"pm_score": 2,
"text": "<p>Essentially, what makes a (mammalian) man a man is a small region on the Y-chromosome called SRY. If this region is deleted, a female phenotype having XY-chromosomes develops. If this region is translocated to an X-chromosome, a male phenotype with two X-c... |
8,862 | <p>As far as I know, just leg bones produce red blood cells. So, how people who lost their both legs produce red blood cells?</p>
| [
{
"answer_id": 8863,
"pm_score": 5,
"text": "<p>Red blood cells are produced in the red marrow which...</p>\n\n<blockquote>\n <p>\"is found mainly in the flat bones, such as the pelvis, sternum,\n cranium, ribs, vertebrae and scapulae, and in the cancellous\n (\"spongy\") material at the epiphyseal e... | [
{
"answer_id": 43959,
"pm_score": 1,
"text": "<p>Red blood cells are produced in the red marrow, and white blood cells are produced in the yellow marrow. The marrow is found in the flat bones (i.e.long bones) which is the pelvis, sternum, ribs, and vertebrae. If the long bones are no longer attached the... |
8,894 | <p>Could cancer be in itself a evolutionary process? Maybe in some way could it be a process of variation? Or would this idea be completely without support, if so, why? </p>
<p>I don't mean that each case would lead to evolution, but that within an entire group of organisms, it could lead to case of of individuals developing ways to resist what caused the cancer, maybe in cases of individuals beating the cancer or in cases of successive generations of off spring from individuals with cancer? </p>
<p>Could it be possible that in rare cases it could lead to the development of new organs or specialized cells?</p>
| [
{
"answer_id": 8900,
"pm_score": 5,
"text": "<p>Interesting question. I believe it definitely is an evolutionary process. unicellularity breaking away from a multicellular life. </p>\n\n<p>There are two examples that I can think of, which can support this argument:</p>\n\n<ol>\n<li>Hela cells: Hela cell... | [
{
"answer_id": 8896,
"pm_score": 3,
"text": "<p>This very interesting question has been explored in a paper, linked this <a href=\"http://evolution.berkeley.edu/evolibrary/news/071001_cancer\">Berkeley page : \"Another perspective on cancer: Evolution within\"</a> (the paper is at the bottom of the page... |
8,901 | <p>Is there any exact definition of vegetable and fruit? How can new plant be classified? </p>
| [
{
"answer_id": 8902,
"pm_score": 4,
"text": "<p>A true fruit is a ripened ovary that usually starts ripening when it is fertilized. And vegetable is any vegetative part of the plant which is edible and contains stored food probably in the form of starch.<br>\nThese definitions are not exact as there are... | [
{
"answer_id": 57299,
"pm_score": -1,
"text": "<p>From a culinary point of view, the difference between a vegetable and fruit is are they sweet or not. </p>\n\n<p>Hence eggplant, tomatoes and bell peppers which are biologically fruits are considered vegetables. </p>\n\n<p>Potatoes which are tubes, are c... |
8,923 | <p>Could a cavity in a human tooth "heal over" or possibly fill back in?</p>
| [
{
"answer_id": 9879,
"pm_score": 4,
"text": "<p>The answer is a simple no. Cavities in the teeth caused by dental decay cannot heal. Enamel which is affected by dental decay cannot heal as they are fully formed at the time of eruption and then on only deteriorates. The deeper part of the tooth which has... | [
{
"answer_id": 8929,
"pm_score": 3,
"text": "<p>Yes, it can be done to a certain degree.</p>\n\n<p><strong>Cementum</strong> is capable of repairing itself to a limited degree and is not resorbed under normal conditions. Some root resorption of the apical portion of the root may occur, however, if ortho... |
8,966 | <p>As stated <a href="http://www.ncbi.nlm.nih.gov/pubmed/19252842">here</a> it is possible to produce fragments of antibodies in bacteria and harvest them (from the medium, I guess, but I don't have access to the full article).
As it is possible to design antibodies, would it be possible and feasible to produce important antibodies large scale through bacteria like it is done for example with insulin?</p>
| [
{
"answer_id": 8970,
"pm_score": 3,
"text": "<p>I'll preface this by saying that I'm talking about antibodies of mammalian/human origin, consisting of two identical heavy and two identical light chains disulfide-bonded into the classic antibody structure:</p>\n\n<p><img src=\"https://i.stack.imgur.com/L... | [
{
"answer_id": 8971,
"pm_score": 1,
"text": "<p>@MattDMo hit the highlights, but I wanted to comment on the creation of libraries of anbitodies for screening in bacatera. But there has been interest in <a href=\"http://www.ablynx.com/en/research-development/nanobody-technology/understanding-nanobodies/... |
8,977 | <p>Inspired by an <a href="https://biology.stackexchange.com/questions/8972/why-must-a-planet-be-in-a-stars-habitable-zone-to-have-life">answer to a previous question.</a></p>
<p>It's hypothesized that extraterrestrial life could be based on silicon rather than carbon as its main structural element.</p>
<p>Are there similar theories about an alternative "life solvent" rather than water? </p>
| [
{
"answer_id": 8970,
"pm_score": 3,
"text": "<p>I'll preface this by saying that I'm talking about antibodies of mammalian/human origin, consisting of two identical heavy and two identical light chains disulfide-bonded into the classic antibody structure:</p>\n\n<p><img src=\"https://i.stack.imgur.com/L... | [
{
"answer_id": 8971,
"pm_score": 1,
"text": "<p>@MattDMo hit the highlights, but I wanted to comment on the creation of libraries of anbitodies for screening in bacatera. But there has been interest in <a href=\"http://www.ablynx.com/en/research-development/nanobody-technology/understanding-nanobodies/... |
8,991 | <p>I saw this article <a href="http://www.ncbi.nlm.nih.gov/pubmed/16710314" rel="nofollow">http://www.ncbi.nlm.nih.gov/pubmed/16710314</a> and it mentioned pA(2) values and I had no idea what they were. What are they? What do they mean? </p>
<p>If possible it'd be just dandy if you could cite some journal articles/books/other reliable sources for me to dig up. </p>
| [
{
"answer_id": 8992,
"pm_score": 3,
"text": "<p>Digging around a bit, I found a few resources:</p>\n\n<p><a href=\"http://www.ncbi.nlm.nih.gov/pubmed/10219974\" rel=\"nofollow\">Design and models for estimating antagonist potency (pA2, Kd and IC50) following the detection of antagonism observed in the p... | [
{
"answer_id": 30590,
"pm_score": -1,
"text": "<p>Below are responses generated using the isolated guinea-pig ileum preparation to determine a pA2 value for a sample of the cholinergic antagonist homatropine.\nResponses are expressed in millimetres +/- SDM (n =4). Plot the data and then determine by Sch... |
8,995 | <p>I know that some birds and marine animals can continue complicated activity (swimming, flying?) while one hemisphere of their brain is asleep.</p>
<p>I'm interested if human brain has some parts of it that can be asleep while others are awake? In other words, <strong>can a human brain be only partially asleep while experiencing insomnia or similar sleep disturbances?</strong></p>
<p>If human brain can have different parts "sleeping" independently of each other, <strong>is it possible that the times to "fall asleep" vary between these different parts of the brain?</strong></p>
<p>I would appreciate research articles on the topic or just the names of brain regions that may exhibit behavior described above.</p>
<p><strong>Update</strong>: I've taken a look at R&K "principles and practice of sleep medicine"' and it mentions the following parts as involved in sleep:</p>
<p>Medulla, preoptic area, hypothalamus, thalamus, entire neocortex involved in NREM.</p>
<p>Neurotransmitter systems: histaminergic, orexinergic, serotonergic, noradrinergic</p>
<p>Sleep factors: adenosine, interleukin-1 and other cytokines, prostaglandin D2, growth hormone releasing hormone, nitric oxide, all promote sleep in or around preoptic area.</p>
<p>This makes me hypothesize that drugs that modify the effects of these systems (ex- caffeine affecting adenosine) could result in sleep- related disturbances in these systems, potentially causing them to fall asleep later that usual. But I'm looking for more info to fihre out if this is true</p>
| [
{
"answer_id": 16999,
"pm_score": 3,
"text": "<p>Reading K&R \"Principles and practice of sleep medicine\" 4th edition, on page 15, under sleep onset I've noticed the following paragraph:</p>\n\n<blockquote>\n <p><strong>Is \"falling asleep\" a unitary event? Our observations suggest that it\n is ... | [
{
"answer_id": 11365,
"pm_score": 3,
"text": "<p>Have you ever tried to read a complicated book after several hours of hard work that required a high concentration? Imagine that you have forced a particular area of your brain. After a hard work, the areas of the brain that we used to finish a work seem ... |
9,000 | <p>My cat was licking my arm with his sandpaper like tongue. It hurt and the area he was licking was slightly smarting afterwards. However, when he licks the palm of my hand the feeling is rather ticklish and results in no pain during or after. </p>
<p>We can pick up sharp, prickly, abrasive objects with our hands (palms/fingers) and even rub against them and have little to no damage incurred. However, if we do the same with say the back of our hand we are more likely to be injured.</p>
<p>I thought maybe the skin is thicker in our palms and that is resulting in our palms being more resilient. But, our palms are so sensitive to touch that it makes me think the skin is thinner to allow the nerves closer access to our environment.</p>
<ul>
<li>Why is there such a stark difference in different areas of skin on our body when it comes to feeling pain and being susceptible to injury from scrapes, bruises, cuts, etc?</li>
</ul>
| [
{
"answer_id": 24692,
"pm_score": 3,
"text": "<p>As dd3 said the density of mechanoreceptors dictates skin sensitivity to touch (also look at <a href=\"http://en.wikipedia.org/wiki/Cortical_homunculus\" rel=\"nofollow\">penfield map</a>. It is a nice illustration of how different senses are mapped to th... | [
{
"answer_id": 106735,
"pm_score": 1,
"text": "<p>There are different receptors and different forces at play here.\nSkin thickness depends primarily on frictional forces and is determined by the thickness of the <a href=\"https://en.wikipedia.org/wiki/Human_skin\" rel=\"nofollow noreferrer\">epidermis</... |
9,001 | <p>As I know, $Cu(OH)_2$ $+$ Protein $\rightarrow$ Purple. So why not use $Cu(OH)_2$ as dye in protein electrophoresis?</p>
| [
{
"answer_id": 24692,
"pm_score": 3,
"text": "<p>As dd3 said the density of mechanoreceptors dictates skin sensitivity to touch (also look at <a href=\"http://en.wikipedia.org/wiki/Cortical_homunculus\" rel=\"nofollow\">penfield map</a>. It is a nice illustration of how different senses are mapped to th... | [
{
"answer_id": 106735,
"pm_score": 1,
"text": "<p>There are different receptors and different forces at play here.\nSkin thickness depends primarily on frictional forces and is determined by the thickness of the <a href=\"https://en.wikipedia.org/wiki/Human_skin\" rel=\"nofollow noreferrer\">epidermis</... |
9,015 | <p>In Skeptics.SE, a question regarding the skulls of children arose. Depicting a scary skull where the permenent teeth are "hidden" inside the jaws and the milk teeth are in the their place.</p>
<p>After all milk teeth fall out, and the permanent teeth "rise", do the holes left by them filled up, or do we go around with holes in our jaws?</p>
<p><a href="https://skeptics.stackexchange.com/questions/9541/is-this-scary-looking-image-about-child-teeth-development-accurate">The question on Skeptics</a></p>
<p>The picture:</p>
<p><img src="https://i.stack.imgur.com/35njF.jpg" alt="picture"></p>
| [
{
"answer_id": 9391,
"pm_score": 4,
"text": "<p>Bone growth continues in the human body for quite awhile after permanent teeth come in. Generally, the complete closure of all growth plates doesn't occur until the mid 20s.</p>\n\n<p>As the top and bottom primary teeth come in, the empty space left behind... | [
{
"answer_id": 9878,
"pm_score": 3,
"text": "<p>This is a skull of a child of around 5 plus years; based on the eruption status and is an example of classic development and eruption pattern of of the teeth at that age. everyone goes through it. It probably looks scary to persons unfamiliar with normal ... |
9,024 | <p>Suppose I'm using 200 nmoles of enzyme and 2 mmoles of substrate. The enzyme should be saturated but if I use 50 mmoles of substrate, the reaction will be faster. Why?
I just can't get it! Even at lower concentration of substrate the enzyme is saturated (all enzyme molecules are engaged in the reaction) but still the reaction rate is lower.</p>
| [
{
"answer_id": 9029,
"pm_score": 3,
"text": "<p>Alan Boyd's <a href=\"https://biology.stackexchange.com/a/9025/948\">answer</a> covers the mechanistic aspects quite well, but there is another aspect he didn't quite touch on - what's going on at the molecular level. To understand this, you need to think ... | [
{
"answer_id": 9025,
"pm_score": 2,
"text": "<p>In terms of Michaelis-Menten kinetics, the rate never reaches the maximum rate:</p>\n\n<p>$v = V_{max} \\times \\frac{S}{K_m + S}$</p>\n\n<p>where $S$ is substrate concentration. Notice that however large $S$ is, the term on the bottom line ($K_m + S$) wil... |
9,026 | <p>My textbook doesn't do a very good job of pointing out what the differences between the two are. It basically mentions axons only in the same breath as the synapse (that synapses are the endings/tips of axons). </p>
| [
{
"answer_id": 9034,
"pm_score": 3,
"text": "<p><a href=\"http://www.gwinnett.k12.ga.us/LilburnES/PromoteGA/biochemistry/Neuron_a_and_d.html\" rel=\"nofollow noreferrer\">This reference</a> is a bit basic, but lists the functions and differences between axons and dendrites. Specifically, dendrites rece... | [
{
"answer_id": 36071,
"pm_score": 1,
"text": "<p><strong><a href=\"http://www.columbia.edu/cu/psychology/courses/1010/mangels/neuro/neurocells/neurocells.html\" rel=\"nofollow noreferrer\">Dendrites</a></strong> </p>\n\n<ul>\n<li>Means <strong><em>Trees</em></strong> in Greek;</li>\n<li>Are the <strong>... |
9,027 | <p>Assume that we have a semi-permeable membrane with water on both sides. First, straightforward, case: On the right side, we have a concentration of the substance A, and on the left side, we have pure water. Obvious effect: water flows from left to right. </p>
<p>Now, imagine we have a second case. We have the same membrane, and a water solution of A to the right. To the left, we have a water solution of a different substance, let's call it B. Now, what happens? I can imagine a few possibilities: </p>
<ul>
<li>the system behaves exactly as in the first case, because the substances have no influence on each other </li>
<li>the system behaves as if it was a solution of A on both sides, with water flowing in the direction of higher concentration (because it only matters if there is something dispersed between the water molecules, but it does not matter what) </li>
<li>some interesting cross-influence effect happens </li>
<li>either one of the three things above can happen, depending on the particular combination of substances A and B</li>
</ul>
<p>Which one is the true effect? What happens, and why? </p>
<p>If you need an example of the actual substances, let B be thiamine and A be plain sodium chloride, but I am interested in the general case. </p>
| [
{
"answer_id": 9030,
"pm_score": 3,
"text": "<p>If A and B are at the same concentration there will be no net movement of water. </p>\n\n<p>Everything is down to diffusion. In your example of solution A/pure water, water molecules on both sides of the membrane are diffusing through the membrane to the o... | [
{
"answer_id": 9538,
"pm_score": 2,
"text": "<p>Actually, the so-called osmolarity of a solution is only determined by the concentration and number of dissociating species in the solute, and is irrespective of the chemical composition of the solute. This is an example of what is known as a <em>colligati... |
9,063 | <p>DNA consists of deoxyribonucleotides, RNA consists of ribonucleotides. They differ mainly (apart from the uracil / thymine difference) in the sugar part, the deoxyribose and the ribose. Those two molecules differ in the hydroxy group in the ribose which is only a single proton in the deoxyribose. This part of the sugar molecule is not directly involved in binding reactions, nevertheless it causes the whole difference in RNA and DNA.</p>
<p>I wonder: could a dNTP be used in an RNA strand (or vice versa)? Is it chemically possible that we have a RNA molecule that contains a dNTP next to its NTPs?</p>
| [
{
"answer_id": 9067,
"pm_score": 3,
"text": "<p>This is rather easy to do if you synthesize oligonucleotides chemically and not enzymatically. This is typically done using <a href=\"http://en.wikipedia.org/wiki/Nucleoside_phosphoramidite\" rel=\"nofollow\">phosphoramidite chemistry</a>, and it allows fo... | [
{
"answer_id": 9066,
"pm_score": 2,
"text": "<p>All DNA polymerases use an RNA primer during DNA replication - they cannot begin a DNA molecule <em>de novo</em>. Before the primer is removed the newly synthesised strand is an RNA-DNA hybrid. The first deoxynucleotide to be incorporated into the new DNA ... |
9,183 | <p>I'm thinking here about environmental disturbance or like climate change-driven warming. It seems as if there are two macroevolutionary ways to deal with environmental change:</p>
<p>1) Have short generation times, and evolve fast. For instance, the mosquito <em>Wyeomyia smithii</em> is under selection by the warming climate in North America and it has shown an evolutionary repsonse. The response is "detectable over a time interval as short as 5 years" (<a href="http://dx.doi.org/10.1073/pnas.241391498" rel="noreferrer">Bradshaw and Holzapfel 2001</a>).</p>
<p>2) Be hardy, and 'try' to wait out changes. No real-world example to cite, but imagine a long-lived tree growing in an area that has become to warm for its seeds to effectively produce seedlings.</p>
<p>It seems intuitively like strategy 1 is better in the case of ongoing climate warming. However, we could easily imagine a 5-year hot spell followed by a return to the normal as part of natural weather variation. Perhaps in this situation strategy 2 is better.</p>
<p>Essentially, having a longevity/generation time/hardiness that matches the time-scale of the disturbance would be important – if the disturbance is long (or unidirectional) compared to your lifespan, evolving fast seems best; if the disturbance is short compared to your life, it seems best to wait it out.</p>
<p>So the question is, is there theory that deals with this? I suspect that I just need to hit the population genetics books again or something; or perhaps there's a massive tome by Gould I should be reading?</p>
<ul>
<li><a href="http://dx.doi.org/10.1073/pnas.241391498" rel="noreferrer"> <strong>Bradshaw WE, Holzapfel CM</strong>. 2001. Genetic shift in photoperiodic response correlated with global warming. PNAS 98: 14509–14511.</a></li>
</ul>
| [
{
"answer_id": 9184,
"pm_score": 3,
"text": "<p>If the disturbance is short compared to a species' lifespan, then it's would be difficult for any adaptations to that disturbance to become fixed. Say an individual with a novel mutation is born during the disturbance that would impart some benefit under s... | [
{
"answer_id": 10236,
"pm_score": 2,
"text": "<p>Not exactly matching your question, but I think that the idea (from stochastic demography) that life histories should be buffered against environmental variability in influential vital rates (<a href=\"http://www.pnas.org/content/95/1/213.abstract\" rel=\... |
9,187 | <p>(sorry, I couldn't resist the rhyming, silly title)</p>
<p>I find it facinating that humans can suffer from an amoeba infestation. Amoeba must reproduce far more slowly than bacteria. In size, they seem to be approximately the same size as the various leukocyte cell types (I see estimates ranging from 10μm to 30μm in diameter). I would assume that they are slow-moving, or, at least no more motile than a leukocyte. </p>
<p>How is it, then, that a population of amoeba can take up residence (and a particularly dangerous one, at that) in a human body without them being wiped out by the immune system? Do we know much about the pathology of such an infection? Do the amoeba actually consume the leukocytes by phagocytosis before they can be consumed themselves?</p>
| [
{
"answer_id": 9194,
"pm_score": 3,
"text": "<p>Assuming you don't mean a single leukocyte as I doubt That a lone leukocyte could do much. Macrophages and neutrophils can release their lytic/degrading enzymes spewing them on to the amoeba. Antibodies produced by BCells, particularly the IgE type can coa... | [
{
"answer_id": 71070,
"pm_score": 1,
"text": "<p>(Yes it is a very old question but I can't resist posting an answer here...)</p>\n\n<p>Not all amoeba are parasites. The common one that cause amoebiasis is <em>Entamoeba histolytica</em>, which can cause diarrhea in some infested individuals. Note that <... |
9,188 | <p>This question is out of curiosity. </p>
<p>The life expectancy of a red blood cell (RBC) is approximately 3 months, and then RBCs are disposed of. Why does the body opt to build new red blood cells rather than using the existing ones? Do RBCs lose functionality/efficiency as they get older?</p>
| [
{
"answer_id": 9192,
"pm_score": 4,
"text": "<p>They are recycled, the iron and other components are broken down and then absorbed. Adaptations of the RBC prevent the same RBC being used. They lack a nucleus to make them highly efficient oxygen carriers (pack as much haemoglobin as possible). Without a ... | [
{
"answer_id": 9239,
"pm_score": 0,
"text": "<p>RBCs do lose their functionality as they get older. In addition to the free radical damage they receive, the cells also become smaller over time which increases the effective concentration of the haemoglobin which causes other problems like hemolysis or ri... |
9,197 | <p>What is the name of a phenomenon where one of the human eyes is seeing brighter/more saturated color than the other? I can observe the same object from the same position while alternating which eye is closed, and there's a visible difference in the saturation of color. Like one color is more pale than the other.</p>
<p>Here's an example of what the difference looks like between image perceived by two eyes:</p>
<p><img src="https://i.stack.imgur.com/j3YKk.jpg" alt="enter image description here">
<img src="https://i.stack.imgur.com/FeeTe.jpg" alt="enter image description here"></p>
| [
{
"answer_id": 9217,
"pm_score": 4,
"text": "<p>here is <a href=\"http://photo.net/casual-conversations-forum/00R4Vd?start=10\" rel=\"noreferrer\">forum discussing similar effect</a> ,</p>\n\n<p>where as similar problem which leads to double vision is single eye is called monocular Diplopia. </p>\n\n<p>... | [
{
"answer_id": 36464,
"pm_score": 3,
"text": "<p>The phenomenon in question is <strong>anisochromatopsia</strong>, however this term is rarely used. This phenomenon is always present, however it is rarely mentioned subjectively, while objective color testing will reveal it easily.</p>\n\n<p>In pathologi... |
9,206 | <p>Eusociality, particularly focusing on the presence of certain altruistic sterile organisms within the social set-up creates questions as to why would the process of natural selection have favoured the persistence of such genes especially in hymenopteric species. One explanation (provided <em>probably</em> by Hamilton) pertains to very similar genetic constitutions of females of such species (owing to haploid nature of males), which increases genetic similarity between the female members of the social group. Thus it would be more "beneficial" (i.e., favourable for the persistence of similar genetic builds) for a female worker to help the fellow siblings, to which it bears greater genetic similarity, than its own offspring to which it bears a lesser genetic similarity. This might in a deeper way explain altruism in case of hymenopterans where the male is a parthenogenetic haploid and the female is diploid. </p>
<p>But why would the sterile condition of the workers in case of almost all eusocial groups be favoured by natural selection on grounds that it improves the 'fitness' of the 'genetic build' of the workers and ultimately the sterile altruists benefit the persistence of its genetic traits? Moreover the altruistic nature of the haploid males also goes unexplained.</p>
| [
{
"answer_id": 9539,
"pm_score": 3,
"text": "<p>I hope I've interpreted your question properly... It's an interesting question, but I think it's important to remember that evolution doesn't act on the two sexes separately. Sterile males might evolve and be maintained simply because they're good for thei... | [
{
"answer_id": 11215,
"pm_score": 3,
"text": "<p>Group selection, in the extreme, yields eusociality due to the shared fate of the replicators in the group. In a multicellular sexual organism, this \"shared fate\" of the \"group\" is the shared prospect that all replicators (alleles) have for making it... |
9,209 | <p>This is the first time I do a centrifuge experiment with my own centrifuge machine, it's just simple made by a rotor that can rotate the tube at high speed. As I know a centrifuge machine can be using for separate biology samples like bacteria, cells, molecules ... But I need some advice to understanding more how to working with it. </p>
<p><a href="https://biology.stackexchange.com/questions/9035/finding-a-template-oligo-combination-for-my-first-pcr-experiment/9037#comment11975_9037">As the suggestion from Alan Boyd</a>, I'm planning to separate <em>Lactobacillus</em> from diluted yogurt. How do I know where the bacteria will be located in the tube after centrifugation (is it usually in bottom ?) and how do I calculate the RPM that is suitable ? And any other interesting diy experiment to do with it ?</p>
| [
{
"answer_id": 9539,
"pm_score": 3,
"text": "<p>I hope I've interpreted your question properly... It's an interesting question, but I think it's important to remember that evolution doesn't act on the two sexes separately. Sterile males might evolve and be maintained simply because they're good for thei... | [
{
"answer_id": 11215,
"pm_score": 3,
"text": "<p>Group selection, in the extreme, yields eusociality due to the shared fate of the replicators in the group. In a multicellular sexual organism, this \"shared fate\" of the \"group\" is the shared prospect that all replicators (alleles) have for making it... |
9,219 | <p>I want to measure OD to know the concentration of dNTP. Any idea for dyeing dNTP at cheapest price and easiest way ? </p>
| [
{
"answer_id": 9220,
"pm_score": 3,
"text": "<p>There may be such a dye, but I'm not aware of it. The standard way to measure dNTPs, and nucleic acids in general is by absorbance at 260 nm. <a href=\"http://webdoc.nyumc.org/nyumc/files/sun-lab/attachments/MBPS.Ch10.pdf\" rel=\"nofollow\">This article</... | [
{
"answer_id": 9222,
"pm_score": 2,
"text": "<p>It will be difficult to achieve the level of wavelength resolution required to differentiate dNTPs, considering that you are doing a DIY experiment. Only very precise spectrophotometers can achieve it and they are expensive.</p>\n\n<p>Another technique you... |
9,240 | <p>I noticed several of these guys outside, all in a vertical position clinging to a wall. I didn't come to them too closely, but my immediate reaction was that they are scorpions.</p>
<p><a href="https://imgur.com/U641JBm" rel="nofollow noreferrer"><img src="https://i.imgur.com/U641JBm.jpg" title="Hosted by imgur.com" /></a></p>
<p>I thought that maybe it's a curled-up scorpion, or maybe there's some kind of particular scorpion that is this circular in shape? These are probably silly conclusions, but I'm not an expert in this field. I would really appreciate the insight of a professional! </p>
<p>thanks very much. </p>
| [
{
"answer_id": 9241,
"pm_score": 4,
"text": "<p>That's the exoskeleton (shed outer shell) of a young cicada, left behind when it emerged as an adult and (we can imagine) flew off somewhere to sing, and find a mate.</p>\n\n<p><a href=\"http://earthsky.org/todays-image/hail-the-17-year-cicada-hatch-of-201... | [
{
"answer_id": 100720,
"pm_score": 3,
"text": "<p>I wanted to add a more thorough answer to this post (with some pictures) since they are bound to get a lot of press (and questions) this summer (2021) -- more on that later....</p>\n<h2>Short answer</h2>\n<p>This is the abandoned exoskeleton (called an &... |
9,243 | <p>I'm currently an undergraduate math student and researching on the internet I discover that exists an area called "biomathematics". Looks so interesting. They use the graph theory and topology to describe the cells and DNA structure. Was love at first sight, because I really love maths and biology.</p>
<p>I'm reading the book "Clinically Oriented Anatomy" of Keith L. Moore and "Essential Cells Biology" of Bruce Alberts, but I don't know if I'm doing right. If anyone know how to start to learn this science I would really appreciate it.</p>
| [
{
"answer_id": 9245,
"pm_score": 3,
"text": "<p>MathsBio is quite a large field. It is an interdisciplinary branch having utility in a lot of branches in biology like biophysics, biomedical, genetics and molecular biology. Applied Mathematics is generally used in modelling and understanding biological ... | [
{
"answer_id": 9269,
"pm_score": 1,
"text": "<p>I really like <a href=\"http://press.princeton.edu/titles/8458.html\" rel=\"nofollow\">\"A Biologist's Guide to Mathematical Modeling in Ecology and Evolution\"</a> by\nSarah P. Otto & Troy Day, although it's more specific to Biology and Evolution - wh... |
9,260 | <p>As i know, Taq Polymerase can be found in Thermus aquaticus, so i do a search for protein list of Thermus aquaticus and have this : <a href="http://www.ncbi.nlm.nih.gov/genome/proteins/1724?project_id=55053" rel="nofollow">http://www.ncbi.nlm.nih.gov/genome/proteins/1724?project_id=55053</a> . After filter for 'polymerase' i found a lot of protein named polymerase :</p>
<ul>
<li>DNA polymerase beta domain protein region</li>
<li>DNA polymerase I</li>
<li>DNA polymerase III, alpha subunit</li>
<li>DNA polymerase III, beta subunit</li>
<li>DNA polymerase III, delta subunit</li>
<li>DNA-directed DNA polymerase
-.....</li>
</ul>
<p>I don't know what they mean and which is the protein i'm looking for ?</p>
<hr>
<p>After click on one of them i have the sequence not in A-T-G-X format :</p>
<p>ORIGIN<br>
1 msgvdallll gvelsraiit aysvyaivli lggflarlpt rweervealg gsfylagvil
61 wryyaggday dldlflrasg mallvlprlv rvvlreyggg r</p>
<p>What does it mean and how to working with it ?</p>
| [
{
"answer_id": 9263,
"pm_score": 3,
"text": "<p>According to <a href=\"http://talon.niagara.edu/~mgallo/391s08web/papers/taq-isolation.pdf\" rel=\"nofollow\">the paper here</a> \"Taq polymerase\" is the DNA polymerase I from <em>Thermus aquaticus</em>. (Incidentally the paper has the complete sequence o... | [
{
"answer_id": 9267,
"pm_score": 0,
"text": "<p>Thank Alan Boyd so much, below is the answer for these protein code mean:</p>\n\n<pre><code> A alanine P proline \n B aspartate/asparagine Q glutamine \n C cystine R arginine \n D aspartate ... |
9,265 | <p>Kefir is a fermented milk drink made with kefir grains. It usually is prepared by inoculating cow, goat or sheep milk with kefir grains.</p>
<p>I would like to prepare the drink with soy milk, which worked fine for some months. Then the kefir grain stagnated in its growth. I use bottled soy milk from the supermarket. I do not produce the soy milk by myself.</p>
<p>In "real" milk the kefir grains never stop growing (and dividing), but in soy milk they apparently do.</p>
<p>Why do the kefir grains stop growing in soy milk? Are they lacking a specific nutrient that is only contained in milk from animals?</p>
| [
{
"answer_id": 19775,
"pm_score": 3,
"text": "<p>Animal Milk. The ideal environment for Kefir Grains is animal milk. Varieties include cow, goat, sheep, and other similar species. Kefir Grains thrive in animal milk due to the chemical makeup of the liquid. The lactose in animal milk provides the most ef... | [
{
"answer_id": 9270,
"pm_score": 3,
"text": "<p>Yes, they are behaving differently because of the lack of nutrients, including lactose, and possibly because of the presence of other chemicals in soy milk that aren't in dairy.</p>\n\n<p>Kefir grains are a complex community of different types of lactic ac... |
9,266 | <p>Does anyone know an effective buffer mix to use for high current Western transfers? We are successfully using the vendor's premixed buffer to transfer a wide range of protein sizes to PVDF membranes at 1A/25V for 10 min. We get great results with the vendor's expensive buffer.</p>
<p>I haven't been able to find a non-proprietary recipe that works. The best ones we have hold the 25V, but then have a decrease in conductivity (increase in resistance) where they will start at 1A, but drop to 0.4A by the end of the 10 min. The vendor's buffer seems to hold the high current and results in better transfers.</p>
<p>I don't know if it will be helpful to list all the variations I've tried in detail, but they have revolved around modifying a traditional Towbin buffer plus SDS, more glycine/Tris, or MgCl2. These were all various suggestions from people around the department, but I haven't found much published evidence for a buffer under these conditions.</p>
<p>I realize 1A (and no I don't mean 1mA) is a lot of current, but the vendor's system works really well. Any pointers on what I might try/add would be appreciated even if you don't have a worked out protocol.</p>
<p>Edit: Info from the MSDS indicates it has 3 reagents:</p>
<pre><code>Listing of dangerous and non-hazardous components:
Proprietary Reagent K
10-20%
Proprietary Reagent EB II
5-10%
Proprietary Reagent S
1.0-2.5%
7732-18-5 water
50-100%
·
.....
Solvent content:
Organic solvents:
0.0 %
Water:
74.8 %
Solids content:
25.2 %
</code></pre>
<p>[I'm not sure if this MSDS info should be put here, just because I'm looking for someone who has already used a high current buffer they know the formulation for, not a guess to what I have.]</p>
| [
{
"answer_id": 14298,
"pm_score": 3,
"text": "<p>So after a lot of work in optimization, I thought I would post what worked best for me. This buffer recipe was able to successfully transfer EGFR and insulin from the same lysate, and a clear band for both (large and small protein respectively). 10% SDS-... | [
{
"answer_id": 9305,
"pm_score": 0,
"text": "<p>The <a href=\"http://en.wikipedia.org/wiki/SB_buffer\" rel=\"nofollow\">SB buffer</a> has been around for quite a while, and I definitely have used it successfully before for both agarose and PAGE gel buffers for some time. The only thing is that you have ... |
9,281 | <p>This is growing in the woods near my house in the Butler, Pennsylvania (USA) area. I have not seen it around before, and I have no idea what is it. What is it? Is it poisonous to pets (or little kids)?</p>
<p><img src="https://i.stack.imgur.com/Zxj5f.jpg" alt="Unknown Plant" />
<img src="https://i.stack.imgur.com/fBnXx.jpg" alt="Unknown Plant" /></p>
| [
{
"answer_id": 9282,
"pm_score": 3,
"text": "<p>That looks like a bit like a Smilax to me, possibly <a href=\"http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242101932\" rel=\"nofollow\"><em>Smilax herbacea</em></a>.</p>\n\n<p>Make sure you have a positive ID on any wild plant before you ... | [
{
"answer_id": 100739,
"pm_score": 2,
"text": "<p><strong>Short answer</strong></p>\n<p>I would also guess it's <em><strong>Smilax herbacea</strong></em>, but let me go a step further and explain why...</p>\n<p><a href=\"https://i.stack.imgur.com/RvuqLm.jpg\" rel=\"nofollow noreferrer\"><img src=\"https... |
9,307 | <p>The picture below shows what I am talking about. Each flower has one and I am just wondering what they are?</p>
<p><img src="https://i.stack.imgur.com/VGxiL.jpg" alt="plant image"></p>
| [
{
"answer_id": 9308,
"pm_score": 2,
"text": "<p>Looking at <a href=\"http://www.orchidireland.ie/images/previews/Orchid_Spur_types.jpg\" rel=\"nofollow\">this</a>, it looks like a spur. A quite overbreed one, though. </p>\n"
}
] | [
{
"answer_id": 9318,
"pm_score": 2,
"text": "<p>These are \"floral spurs\" – they usually contain nectar, and are part of the variety of complex flower shapes that orchids and other flowers, like columbines, have co-evolved with their pollinators.</p>\n\n<p>Essentially, in order for the pollinator to re... |
9,326 | <p>What does phasing mean in genetics/informatics? I've heard that a phased file is a file that has genes separated by chromosome, but can someone give a concrete definition of what phasing actually means?</p>
| [
{
"answer_id": 9327,
"pm_score": 4,
"text": "<p>This refers to <a href=\"http://en.wikipedia.org/wiki/Haplotype\">haplotype</a> phase (aka <a href=\"http://en.wikipedia.org/wiki/Gametic_phase\">gametic phase</a>). This essentially means knowing which allele belongs to which copy of the chromosome, or al... | [
{
"answer_id": 74107,
"pm_score": 0,
"text": "<p>phasing is the relationship between adjacent alleles on the same chromosome i.e. if they are in cis or trans configuration. In other words, weather two alleles are indeed on the same chromosome or on different chromosome. One of the reason alleles get shu... |
9,342 | <p>Assuming the current model of human evolution to be correct, approximately when did the earliest ancestor of humans live, who was intelligent enough, that if raised from a young enough age, could learn the necessary skills to live in today's society:</p>
<ul>
<li>learn a modern language</li>
<li>learn to read and write</li>
<li>learn to use most common tools and household items</li>
<li>learn to drive a car, use a telephone, a computer, have an average job.</li>
</ul>
| [
{
"answer_id": 15669,
"pm_score": 3,
"text": "<p>Interesting question.</p>\n\n<p>The organism would have to be monogamous, that's for sure, otherwise it would be too competitive and it would be a beast - as chimps are. Chimps couldn't integrate into the modern society.</p>\n\n<p>So, monogamy is the prim... | [
{
"answer_id": 54611,
"pm_score": 0,
"text": "<p>Well... given than mitochondria eve was around 99–148 thousand years ago <a href=\"https://en.wikipedia.org/wiki/Mitochondrial_Eve\" rel=\"nofollow noreferrer\">https://en.wikipedia.org/wiki/Mitochondrial_Eve</a> The human species is at least that old. </... |
9,352 | <p>Just what the title states. The thought came from reading <a href="https://biology.stackexchange.com/questions/2705/when-has-an-organism-evolved-enough-to-be-called-a-new-species">When has an organism evolved enough to be called a new species?</a></p>
<p>I'm probably wrong but I understand new species happen sporadically rather than in whole-sale lot during breeding season. Is the new species capable of breeding with members of its parent species? How does a new species survive inbreeding initially?</p>
| [
{
"answer_id": 9354,
"pm_score": 4,
"text": "<p>Well, speciation is a process, not a single event thing. </p>\n\n<p>Usually what happens initially is geographic isolation of some members of a species, so in that sense the inbreeding is something that is influencing and you can also think of it as causin... | [
{
"answer_id": 9633,
"pm_score": 0,
"text": "<p>This is indeed a very good question, that I have spent a long time thinking about myself. My take on this is that there is indeed a very close relationship between inbreeding and speciation, but that inbreeding actually PRECEDES speciation ! The key to th... |
9,377 | <p>In the beginning of meiosis, there is one cell. During meiosis, 1 cell divides into 4 cells. Does each of these 4 cells divide each into 4 more cells?</p>
| [
{
"answer_id": 9378,
"pm_score": 3,
"text": "<p>No, meiosis is not a cycle like mitosis. In mitosis, haploid or diploid cells divide to create two genetically identical cells, and this process can go on and on. On the other hand, meiosis results in 4 genetically unique daughter cells which are also hapl... | [
{
"answer_id": 9449,
"pm_score": 1,
"text": "<p>In species where an individual can be haploid (for example in <a href=\"http://en.wikipedia.org/wiki/Haplodiploid\" rel=\"nofollow\">haplodiploidy</a>) then cells produced by meiosis do multiply by mitosis in order for the individual to grow.</p>\n\n<p>Fro... |
9,382 | <p>Found in Russia, in the kitchen. It is about 1–2 cm length.</p>
<p><a href="https://i.stack.imgur.com/gc5QK.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/gc5QK.jpg" alt="unknown insect"></a></p>
<p><a href="https://i.stack.imgur.com/pcc8P.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/pcc8P.jpg" alt="unknown insect"></a></p>
| [
{
"answer_id": 9383,
"pm_score": 4,
"text": "<p>This is an immature \"True Bug\", order Hemiptera. You can tell this from the general shape of the wings, and from the big \"beak\", a feature of the Hemiptera.</p>\n\n<p>Within Hemiptera, it's possible that with those enlarged front legs, it could be an A... | [
{
"answer_id": 10755,
"pm_score": 1,
"text": "<p>It may also be a squash bug, they look pretty similar. They even have enlarged front legs too.</p>\n"
}
] |
9,406 | <p>I found this in Russia. It is approximately 2cm long.</p>
<p><a href="https://i.stack.imgur.com/QXtQy.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/QXtQy.jpg" alt="unidentified insect photo 1"></a></p>
<p><a href="https://i.stack.imgur.com/5vTrV.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/5vTrV.jpg" alt="unidentified insect photo 2"></a></p>
| [
{
"answer_id": 9421,
"pm_score": 4,
"text": "<p>This is a wasp, (see that nice slim \"wasp waist\" it's got?), which means taxonomically that it is in the order Hymenoptera (which it shares with bees and ants).</p>\n\n<p>Within Hymenoptera, wasps are diverse and often difficult to ID, but it's possible ... | [
{
"answer_id": 36943,
"pm_score": 2,
"text": "<p>Since it got bumped and no one seemed to be too clear on an identification. Based on the presence of two recurrent veins in the forewing, following identification guidelines <a href=\"http://jenny.tfrec.wsu.edu/opm/displaySpecies.php?pn=920\" rel=\"nofoll... |
9,477 | <p>When humans give birth, more than often medical assistance is needed. Others gather around and frantically look for any way to help. But when an animal gives birth, it is usually seen as a moment where you give the female its space and let the birth occur naturally and without any assistance. The animal is of course in serious pain just as a female human but this is more than often not taken into account. Why is it that animal births are not taken as seriously?</p>
| [
{
"answer_id": 9499,
"pm_score": 4,
"text": "<p>Our heads are bigger.</p>\n\n<p>There's <a href=\"http://www.pnas.org/content/106/23/9125.extract\" rel=\"nofollow\">some</a> <a href=\"http://www.sciencedaily.com/releases/2012/08/120827152037.htm\" rel=\"nofollow\">debate</a> on the issue, but in essence... | [
{
"answer_id": 9480,
"pm_score": 2,
"text": "<p>And, if your question pertains to \"seen by animals of the same species\", there are at least anecdotal accounts of animal-assisted births, as in <a href=\"http://io9.com/5983426/zoologists-watch-as-monkey-midwife-delivers-baby\" rel=\"nofollow\">this case... |
9,487 | <p>Why are my faeces black in colour the morning after I eat some <strong>Oreos</strong>? </p>
<p><strong>Day 1</strong> : Eat a handful of Oreos & the next morning your stool is black.<br>
<strong>Day 3</strong> : Eat a handful of cocoa flavored biscuits & the next morning your stool is normal.<br>
<strong>Day 5</strong> : Eat a handful of Chocolates & the next morning your stool is normal.</p>
<p><a href="http://www.thenakedscientists.com/HTML/questions/question/2494/" rel="nofollow noreferrer">I'm aware of the beetroot digestion story</a>, and how it doesn't happen to everyone. What is surprising in the case of Oreos is that it just takes a
handful of Oreos to turn the stool black. But with any other biscuits or chocolates, my faeces are normal.</p>
<p>I don't have anything other than anecdotal evidence but a lot (<strong>NOT ALL</strong>) of my friends have had similar experience. Just Googling "<strong><a href="http://www.google.com/search?q=Black+stool+after+eating+Oreos" rel="nofollow noreferrer">Black stool after eating Oreos</a></strong>" & I see a lot of people (not all) having similar experience. Do note that to my knowledge it doesn't affect my body in any way.</p>
<p>Why is that the case? Why doesn't it happen to everybody?
What ingredient in Oreos makes it happen? What is the physiological underpinning?
Asking this question with curiosity than caution. Looking for biological/biochemical perspective.</p>
| [
{
"answer_id": 13710,
"pm_score": 3,
"text": "<p>This is a perfectly reasonable question based on a self-adminstered (human) trial. Morever, the proposer bases their observations not on one subject but several reports. The impromptu survey of friends etc. is also acceptable. By the way, self-reported in... | [
{
"answer_id": 61205,
"pm_score": 0,
"text": "<p>According to <a href=\"http://www.thekitchn.com/for-truly-dark-chocolate-baked-goods-black-cocoa-powder-ingredient-spotlight-173923\" rel=\"nofollow noreferrer\">this site</a> there is something called black cocoa powder, a particularly dark product refer... |
9,492 | <p>An American is staying in my house for the summer and claims that food (specifically, bread and milk) spoils a lot faster here than at home in California. Is there a significant difference in chemical content (preservatives etc.), or other factors, that might explain this? </p>
| [
{
"answer_id": 9497,
"pm_score": 4,
"text": "<p>I would think added preservatives are the most likely candidate, for example, Azodicarbonamide is frequently added to bread in the US, but banned in Ireland and most of the rest of the EU. Since it has a preservative effect it is a reasonable candidate for... | [
{
"answer_id": 9495,
"pm_score": 2,
"text": "<p>There are more factors than we can ever consider. </p>\n\n<p>As far as region: does California represent all of the US? What part of California? What part of Ireland? What's the humidity and average temperature of each region? What are the agricultural... |
9,512 | <p>I have read about cortical circuits in the context of connectomics (e.g. any example <a href="https://www.google.com/search?q=cortical%20circuits%20connectomics#sclient=psy-ab&q=%22cortical%20circuits%22%20%20connectomics&oq=%22cortical%20circuits%22%20%20connectomics&gs_l=serp.3...5544.7332.0.7501.3.3.0.0.0.0.64.167.3.3.0....0.0..1c.1.20.psy-ab.AAgDLCcYx5k&pbx=1&bav=on.2,or.r_cp.r_qf.&bvm=bv.49967636,d.dmg,pv.xjs.s.en_US.jOYpRJj4zMA.O&fp=332b6c997d1bae1d&biw=1200&bih=1754" rel="nofollow">here</a>) and computational neuroscience (e.g. any example <a href="https://www.google.com/search?q=computational%20neuroscience#sclient=psy-ab&q=computational%20neuroscience%20%22cortical%20circuits%22%20&oq=computational%20neuroscience%20%22cortical%20circuits%22%20&gs_l=serp.3...7052.7052.0.7472.1.1.0.0.0.0.57.57.1.1.0....0.0..1c.1.20.psy-ab.T0CItQP16pQ&pbx=1&bav=on.2,or.r_cp.r_qf.&fp=332b6c997d1bae1d&biw=1200&bih=1754&bvm=pv.xjs.s.en_US.jOYpRJj4zMA.O" rel="nofollow">here</a>), but a simple Google/Wikipedia does search not show an exact definition.</p>
<p>What exactly is a cortical circuit?</p>
| [
{
"answer_id": 9523,
"pm_score": 3,
"text": "<p>I may be simplifying this, but I think it's just a fancy schmancy way of referring to the electrical \"circuits\" found in the brain, in this case the cortex (overall, or more specifically motor, visual, etc., as the case may be). <a href=\"https://en.wik... | [
{
"answer_id": 9533,
"pm_score": 2,
"text": "<p>The term \"cortical circuit\" refers to the generalization that the neocortex is a uniform structure. For the most part, the outer sheet of the brain (the neocortex) is the same structure of neurons all the way around the brain. It consists of the canonic... |
9,558 | <p>Is there a term I can use to refer collectively to both exons and introns? By collectively, I don't mean ligated as with an unprocessed transcription product. I'm just writing about exons and introns and getting frustrated that I keep on having to write "exons and introns", wishing there was a more concise term I can use in the place of that phrase.</p>
<p>For example, the term I am looking for would fill in the following blank perfectly.</p>
<blockquote>
<p>The gene has 5 exons and 4 introns, so it has 9 <strong><em>_</em>____</strong>.</p>
</blockquote>
| [
{
"answer_id": 9560,
"pm_score": 4,
"text": "<p>How about \"splicing fragments\"? It might be easier to refer to them according to the mechanism of production.</p>\n"
}
] | [
{
"answer_id": 9564,
"pm_score": 1,
"text": "<p>I think your best bet would be <em>transcript</em>. <em>Gene</em> is actually quite close but most of the current definitions include the promoter sequence in the gene so that is not restricted to introns and exons. </p>\n\n<p>Transcripts, on the other han... |
9,601 | <p><strong>Question</strong></p>
<p>Quite a few plant species can be used for medicinal purposes <a href="http://en.wikipedia.org/wiki/List_of_plants_used_in_herbalism" rel="noreferrer">wiki</a>. As an example, <em>Filipendula ulmaria</em> is rich in acetylsalicylic acid (aspirin).</p>
<p>An allele that produces a substance which is beneficial for a predator should not get fixed in the population! <em>Why are there so many drug-like plants?</em></p>
<hr>
<p><strong>Thoughts</strong></p>
<p>Here are some (intuitive, unclear or far-fetched, non-exhaustive and non-exclusive) hypotheses I can think of:</p>
<ol>
<li><p>Because plants want their seeds to get ingested in order to propagate</p></li>
<li><p>Is it because there are so many substances that affect our homeostasy that many plants are toxic and many are healthy just by chance. Containing healthy substances are not adaptations but by-product of evolution.</p></li>
<li><p>The substances that are beneficial for us actually evolved to repulse predators. These substances are toxic at high dosage and therefore are efficient against predators that are small or eat a lot of plants (herbivorous). These substances at low dosage might actually have a benefical effect. For example a substance that make blood thicker is very toxic except if you eat just a bit of it while bleeding.</p></li>
<li><p>We (primate or whatever taxon you want to consider) evolved in order to get advantage of the surrounding envirronment. Sbstances that were neutral became beneficial. The advantage of being sensitive to various products cause that, by chosing our food source, we can heal. Therefore, by evolving sentivity to various substances, our behaviour can act as a reinforcement to immunity (and other anti-illness system). If this is true, we might expect that the frequency of presence of a plant species affect the probability that out homeostasy get affected when eating it.</p></li>
<li><p>Lineage selection. Lineages that produce substances that are active in predators body in a way or another are undergoing many various selection forces because of these substances. Therefore they get a higher speciation rate than other lineages.</p></li>
<li><p>Keeping some non-herbivorous species in large population size (by helping them) is the best way to keep herbivorous species in small population (because of territory competition, predators relationships, etc... ) </p></li>
</ol>
| [
{
"answer_id": 9603,
"pm_score": 5,
"text": "<p>Perhaps the question may also be phrased, \"Why is it common for plants to produce chemicals that possess pharmacological or toxicological effects in man and animals?\", and to that question it is often reasoned that plants, being sessile and otherwise def... | [
{
"answer_id": 9602,
"pm_score": 3,
"text": "<p>Firstly, most plants or other natural medicinals existed way before we knew about them; it's not that plants mimic drugs, its that drugs mimic plants.</p>\n\n<p>To answer your question succinctly, compounds that we can use for our own medical benefit often... |
9,639 | <p>I have read many papers that refer to cell type, cell state and cell function, but I haven't found an explicit definition for each of these terms.</p>
<p>For example <a href="http://vir.sgmjournals.org/content/75/9/2367.full.pdf" rel="nofollow">this paper</a> (Brown et al. 1994. <em>J General Virology</em> 75: 2367-2377) refers to cell type and cell state without providing an explicit definition of both terms. I have a vague idea of what these terms mean but a more explicit definition would help me greatly in understanding them.</p>
| [
{
"answer_id": 9642,
"pm_score": 3,
"text": "<p>Mainly cell type refers to the differentiation degree to form a cell population whose characteristics are identifiable by using simple microscopy, stains or immunological methods. Examples of cell types would be T8 lymphocytes, peripheral astrocytes or hep... | [
{
"answer_id": 107558,
"pm_score": 1,
"text": "<p>I'm busy writing a section on this topic for a dissertation and have run into the following useful definition, which I'll write here for posterity:</p>\n<ul>\n<li>Cell type and state can be thought of as a location in "state space", a virtual l... |
9,662 | <p><a href="https://en.wikipedia.org/wiki/Color_blindness#Red.E2.80.93green_color_blindness" rel="nofollow noreferrer">https://en.wikipedia.org/wiki/Color_blindness#Red.E2.80.93green_color_blindness</a></p>
<blockquote>
<p>Protanopia (1% of males): Lacking the long-wavelength sensitive retinal cones, </p>
</blockquote>
<blockquote>
<p>Deuteranopia (1% of males): Lacking the medium-wavelength cones, </p>
</blockquote>
<p>Do they lack <em>all</em> those cones, or are they just (severely) short? </p>
<p><a href="https://biology.stackexchange.com/questions/9662/do-colorblinds-have-less-cones-or-no-cones-of-a-certain-type"></a>
<a href="https://biology.stackexchange.com/questions/9663/colorblinds-can-match-any-colors-with-some-mixture-of-just-two-primary-colors"></a></p>
| [
{
"answer_id": 17896,
"pm_score": 2,
"text": "<p>This is a complicated case, as it can have multiple causes.\nThe genes which are coding for the long (L, yellow) and medium (M, green) wavelength photopigments are located head-to-tail on the X chromosome. This is the reason why this colors are affected m... | [
{
"answer_id": 17860,
"pm_score": 0,
"text": "<p>You need to have faulty cones or be completely devoid of the cones that help you perceive a particular colour. If you do possess cones to visualize a colour, you aren't technically colour blind because you should still be able to detect the colour slightl... |
9,669 | <p>The point of my question is not to talk about events that are uncontrolled by living organisms. My question is about controlled randomness, or I'd like to say adaptive random process. Process that are random because it was selected in order to be random.</p>
<p>The first thing that pop in my mind when thinking of "adaptive random process" in biology is Fair Meiosis. <strong>Do you have other examples of "adaptive random process"?</strong> An individual might display a random behaviour in order to avoid that others to predict its future behaviour. Is there any evidence for such things? Do you know any other evidence on what I called "adaptive random process"?</p>
| [
{
"answer_id": 9672,
"pm_score": 3,
"text": "<p>In an evolution mutations are often random and lead to differences in phenotype that can be adaptive under certain pressures. A lot of times mutation is a random process, but here are three cases I can think of off of the top of my head where I would say ... | [
{
"answer_id": 45593,
"pm_score": 1,
"text": "<p>I know of an example in development biology. <a href=\"http://www.math.uci.edu/~qnie/Publications/ja67.pdf\" rel=\"nofollow\">Here is an example where noise in retinoic acid gradients is required for the boundaries in the developing hindbrain to sharpen</... |
9,670 | <p>How and why did Fair Meiosis evolve?</p>
<p>I can hardly think that it provided a fitness advantage to the individual carrying the mutation. Why would it? Or did it evolve through lineage selection? Or was it some kind of pre-existing characteristic of meiosis that have no energy cost and therefore never disappear?</p>
<p>UPDATE:</p>
<p>I call fair meiosis the process of meiosis in which each chromosome has an equal chance of transmission.</p>
<p>I'm trying to make my questions clearer.</p>
<p>Is there any selection pressure in favour of alleles causing a fair meiosis? If yes, why? It doesn't seem to me to provide any advantage to the individual carrying this allele.</p>
| [
{
"answer_id": 9675,
"pm_score": 2,
"text": "<p>There's a more meta-level discussion on meiosis, which is that there is an advantage for genes which can get themselves selected in meiosis more often would prosper. This is a prediction of the biologist Robert Trivers, working with Bill Hamilton in the l... | [
{
"answer_id": 9674,
"pm_score": 2,
"text": "<p>I think that <em>Fair meiosis</em> (I assume that you are referring to that chromosomes have an equal chance of transmission) can be seen as a byproduct of recombination at meiosis, which makes every chromosome a mosaic of maternal and paternal chromosomes... |
9,677 | <p>In certain species only the dominant male gets to mate (or given strong preference), and yet the sex ratio remains 1:1. (I'm thinking in particular of gorillas). How does this happen? It doesn't seem like Fisher's argument should apply in this case.</p>
| [
{
"answer_id": 9678,
"pm_score": 5,
"text": "<p><a href=\"http://en.wikipedia.org/wiki/Fisher%27s_principle\">Fisher's principle</a> applies to such cases as much as it does to species where only pairs mate. Consider a species where a successful male has exclusive mating with a harem of 20 females, and... | [
{
"answer_id": 9683,
"pm_score": 2,
"text": "<p>mgkrebbs has already covered the maths that leads to the preservation of ratio, so I'll not recap.</p>\n\n<p>You might have noticed that the argument only remains true if you don't know whether the particular male you produce is likely to be the dominant m... |
9,684 | <p>The official <a href="http://www.genenames.org/data/hgnc_data.php?hgnc_id=30224">HUGO gene nomenclature</a> page says that GPR172A (Gamma-hydroxybutyrate receptor) and SLC52A2 (riboflavin transporter, member 2) are the same. The sequence reported by <a href="http://www.fasebj.org/content/21/3/885">Andriamampandry</a> seems to be the same, but I find no other evidence. Can anyone enlighten me? </p>
<p>(I'm wondering if I should add the <a href="http://en.wikipedia.org/wiki/Template%3aPBB/79581">SLC52A2 information</a> to the <a href="http://en.wikipedia.org/wiki/GHB_receptor">GHB receptor Wikipedia page</a>.)</p>
| [
{
"answer_id": 9728,
"pm_score": 4,
"text": "<p>This isn't a case of gene splicing causing different protein variants. In the studies that identified these two functions (GHB sensitivity and riboflavin transport), they were using DNA derived from mRNA (cDNA), which means what was being expressed in the... | [
{
"answer_id": 9706,
"pm_score": 1,
"text": "<p>Its fairly common for a gene to have multiple names. I cant say for certain, but Jax and GeneCards also lists them as being synonymous so I would say its safe to say they are the same</p>\n\n<p><a href=\"http://www.informatics.jax.org/marker/MGI:1289288\" ... |
9,689 | <p>What is a genomic imprint? How does genomic imprinting take place?</p>
<p>If I say that "this" allele is maternally imprinted does it mean that the allele of the gene is passed only by the mother? If a pedigree is given, how can we identify whether the trait is paternally imprinted or maternally imprinted?</p>
<p>Please try to explain all this in as simple words as possible.</p>
| [
{
"answer_id": 9761,
"pm_score": 3,
"text": "<blockquote>\n <p>**** \"What is a genomic imprint? How does genomic imprinting take place?\"**</p>\n</blockquote>\n\n<p>Genomic imprinting is an <a href=\"http://en.wikipedia.org/wiki/Epigenetics\" rel=\"nofollow noreferrer\">epigenetic</a> mechanism of in... | [
{
"answer_id": 9695,
"pm_score": 0,
"text": "<p>It is incorrect to say that a trait is imprinted, although the phrase is often used. I will simplify this by talking about just two chromosomes. A mammal will have one chromosome from mother and one that is nearly identical inherited from the father. Th... |
9,715 | <p>Humans have very strict tradition of hygiene, such as washing hands before eating, using utensils, and in general keeping as much distance between food and dirt as possible.</p>
<p>At the same time, most animals would eat off the floor or eat food with foreign particles stuck to it ( after being dropped on the floor). Many animals, like cats groom themselves, practically licking off (and swallowing?) dirt off their coats.</p>
<p><strong>Do animals suffer adverse effects, such as indigestion or disease from consuming food that is dirty by human standards?</strong></p>
<p>Or is it something about the human digestive system that cannot handle the same kinds of dirt that animals can?</p>
| [
{
"answer_id": 9719,
"pm_score": 5,
"text": "<p>I'm sure it varies wildly based on the animal and what they're eating. In general, if in the course of an animal's natural feeding process it picks up a little dirt, it has evolved to cope with that. Animal's behaviors and guts have evolved to fit their ... | [
{
"answer_id": 9733,
"pm_score": 2,
"text": "<p>Animals certainly occasionally get sick from eating contaminated food, just as humans used to before our standards of sanitation improved. There are various adaptations/considerations for this. Apologies for not being able to find scholarly references. He... |
9,726 | <p>I digested two plasmids, one with EcoRI and AgeI and the other with EcoRI and XmaI. Digests looked as expected, so I purified the respective fragments and set up the T4 DNA ligation (AgeI and XmaI sites are compatible).</p>
<p>After E.coli transformation, culture and miniprep from 12 of the resulting cultures, I digested the isolate from the minipreps with BclI to confirm I had the correct product (because there was one BclI site in the insert and another one in 1.4kb away in the backbone). The results of this digest clearly show that there are two different ligation products: four lanes share one banding pattern and the other eight share a pattern which is different from it.</p>
<p>I checked both plasmids for other restriction sites of the enzymes used which I overlooked before, but found none. Because EcoRI and XmaI/AgeI sites are radically different (AATT vs. CCGG), I would exclude the possibility of the insert being ligated in reverse orientation.</p>
<p>Are there any common causes of unexpected ligation variants besides unnoticed restriction sites and reverse ligation?</p>
| [
{
"answer_id": 9841,
"pm_score": 1,
"text": "<p>A second investigation has suggested that the ligation product in question was indeed the vector, without ligated insert!</p>\n\n<p>The vector also contained a BamHI site close to the XmaI site, so in a subsequent digest with EcoRI and BamHI, I was expecti... | [
{
"answer_id": 9732,
"pm_score": 2,
"text": "<p>Could be insert polymerization. If you have your stretch of DNA like this:</p>\n\n<pre><code> (5')-AATTagctagcatcgtgatcgacg-(3')\n ||||||||||||||||||||\n (3')-tcgatcgtagcactagcagcGGCC-(5')\n</code></pre>\n\n<p>And you take that, flip it aroun... |
9,742 | <p>Can anyone identify the plant below? It's in a backyard in Pennsylvania, and the photo was taken today.</p>
<p><img src="https://i.stack.imgur.com/8WHLK.jpg" alt="enter image description here"></p>
| [
{
"answer_id": 9746,
"pm_score": 3,
"text": "<p>Those flowers don't come from the same plant as that big leaf in the front do they? Cant help you with the leaves, but the flower looks like a <a href=\"http://en.wikipedia.org/wiki/Daylily\" rel=\"nofollow noreferrer\">daylily</a>. source: I know nothing... | [
{
"answer_id": 13954,
"pm_score": 1,
"text": "<p>The flower is a <em>Hemerocallis fulva</em> (Hemerocallidaceae).</p>\n\n<p>The leaf seems to be a Cucurbitaceae, as said above, the same family as the zucchini</p>\n"
}
] |
9,750 | <p>I know there is some mechanism in humans by which we start to ignore a certain stimuli if it persists for a long time (e.g., we don't feel our shoes all the time !).</p>
<p>Can the same thing happen in <em>Mimosa pudica</em>? Can it again get it's original arrangement of leaves if it is stimulated without interruption?</p>
<p>I think it should do this, otherwise it will not be able to grow if it is surrounded by bushes from all the sides as it will be stimulated constantly and so will be unable to photosynthesize properly. </p>
| [
{
"answer_id": 9746,
"pm_score": 3,
"text": "<p>Those flowers don't come from the same plant as that big leaf in the front do they? Cant help you with the leaves, but the flower looks like a <a href=\"http://en.wikipedia.org/wiki/Daylily\" rel=\"nofollow noreferrer\">daylily</a>. source: I know nothing... | [
{
"answer_id": 13954,
"pm_score": 1,
"text": "<p>The flower is a <em>Hemerocallis fulva</em> (Hemerocallidaceae).</p>\n\n<p>The leaf seems to be a Cucurbitaceae, as said above, the same family as the zucchini</p>\n"
}
] |
9,787 | <p>A virus can either participate in a lysogenic cycle or a lytic cycle. What decides that?</p>
| [
{
"answer_id": 9794,
"pm_score": 3,
"text": "<p>It depends on a few factors, such as how many phages infected the cell, whether or not the cell is in good growth conditions, and so on. If the cell is in stress or has low amounts of nutrients, the lysogenic pathway is typically activated.</p>\n\n<p>The u... | [
{
"answer_id": 71184,
"pm_score": -1,
"text": "<p>The term “lysogenic” implies that prophages are capable of giving rise to active phages that lyse their host cells. This occurs when the viral genome exits the bacterial chromosome and initiates the lytic cycle. The triggers for this switch-over are us... |
9,791 | <p>Before the discovery of <em>Australopithecus afarensis</em> in the 1970s, most anthropologists believed that an increase in brain capacity had preceded bipedal locomotion. However, this <a href="http://en.wikipedia.org/wiki/File%3aLucy_Skeleton.jpg" rel="nofollow">reconstruction of the Lucy skeleton</a> shows that the <em>A. afarensis</em> was bipedal even with a brain size of around 400 cc.</p>
<p>But the <a href="http://en.wikipedia.org/wiki/File%3aLucy_blackbg.jpg" rel="nofollow">actual Lucy skeleton</a> does not include feet, and only has two partial leg bones.</p>
<p>How do anthropologists determine, based on the bones preserved, that <em>A. afarensis</em> was bipedal?</p>
| [
{
"answer_id": 9796,
"pm_score": 5,
"text": "<p>Mainly because of the characteristics of the pelvic joint with the femur and the foramen magnum (the hole the spinal cord uses to connect with the encephalon). Also, there are more specimens other than Lucy, and there also exist fossil footprints (for inst... | [
{
"answer_id": 26330,
"pm_score": 0,
"text": "<p>This is a great question and one we should all be asking. Given that our closest relatives the great apes are all quadrupedal, our ancestors at one point must have also been quadrupedal. In fact we as humans are mainly quadrupedal between our first nine t... |
9,850 | <p>Walking past the park today, I heard a cicada so loud I thought at first it must be some sort of large power tool. How is it that that very small animals like cicadas (crickets, etc.) can make such loud sounds? It seems intuitive that larger animals should be able to make louder sounds, but perhaps:</p>
<p>a) I just fundamentally misunderstand the physics involved</p>
<p>b) A theoretical larger animal <em>should</em> be able to make louder sounds, but cicadas are just extremely efficient, making up for their small size</p>
<p>c) ?</p>
| [
{
"answer_id": 19632,
"pm_score": 5,
"text": "<p><strong>The Cicada</strong></p>\n\n<p>A careful study of the noise-making apparatus of the cicada can be found in a 1994 paper by Young and Bennet-Clark.$^1$ The authors generated sounds at about 0-16 kHz at peaks on the order of 100 dB using cicadas in v... | [
{
"answer_id": 19666,
"pm_score": 2,
"text": "<p>intuitively, I would say that small creatures are not seen easily. therefore they need audible lighthouses to signal to others their location</p>\n\n<p>big creatures don't usually have this need, though some do such as whales which can emit sounds heard h... |
9,916 | <p>I think the main reason is the natural selection that is causing methicillin-resistance.
However, I am not completely sure what this means practically.</p>
<p>Here, the original question:</p>
<p>MRSA was isolated in the throat secretion of patient hospitalized with bronchitis. Which of the following
statements best characterizes this microorganism?</p>
<ul>
<li>a. its MIC is increased to methicillin, but not to penicillin</li>
<li>b. methicillin-resistance is associated with production of β-lactamases</li>
<li>c. Methicillin-resistance is caused by changes in configuration (mutation) of PBP</li>
</ul>
<p><strong>What is the right answer?</strong></p>
| [
{
"answer_id": 9935,
"pm_score": 3,
"text": "<p>I think you can normally think about similar pressures leading to extended-spectrum beta-lactamase (ESBLs) and methicillin/oxacillin-resistant Staphylococcus aureus (MRSA). </p>\n\n<p>Going to the core of your question: </p>\n\n<p><a href=\"http://dx.doi... | [
{
"answer_id": 9995,
"pm_score": 0,
"text": "<p>Acquisition of a new PBP (eg methicillin resistance in staphylococcus aureus), source Murray.</p>\n\n<p>So I think the answer is C: change in configuration (mutation) of PBP, which can interpreted as acquisition of a new PBP.</p>\n"
}
] |
9,921 | <p>What information is greatly lacking which does not allow us to propose a solid theory for origin of life ?</p>
| [
{
"answer_id": 9923,
"pm_score": 4,
"text": "<p>First of all, we <a href=\"http://en.wikipedia.org/wiki/Abiogenesis\">do have</a> some solid theories to explain the origin of life. That said, the main thing missing in order to be able to accept one of these theories with a decent amount of certainty is ... | [
{
"answer_id": 66706,
"pm_score": -1,
"text": "<p>The reason for no single, solid origin of life (OOL) theory is that there are \nmany and none of them explain or resolve the overall or the detailed issues of OOL, encompassing wide differential and even conflicting approaches, e.g., reproduction vs meta... |
9,937 | <p>After researching the definition of Assay, I am left with the idea that an assay refers to scientific screening. It could be of chemicals, microbes, etc.</p>
<p>I understand that during drug-discovery assays scientists screen for chemical compounds that may make up an effective drug.</p>
<p>But could someone explain, or provide me with some links that further discuss the process of assays, or how they work or take place during drug discovery?
Frankly, I'm also still a bit confused about the definition of "Assay" itself.</p>
<p>Thank you.</p>
| [
{
"answer_id": 9923,
"pm_score": 4,
"text": "<p>First of all, we <a href=\"http://en.wikipedia.org/wiki/Abiogenesis\">do have</a> some solid theories to explain the origin of life. That said, the main thing missing in order to be able to accept one of these theories with a decent amount of certainty is ... | [
{
"answer_id": 66706,
"pm_score": -1,
"text": "<p>The reason for no single, solid origin of life (OOL) theory is that there are \nmany and none of them explain or resolve the overall or the detailed issues of OOL, encompassing wide differential and even conflicting approaches, e.g., reproduction vs meta... |
9,944 | <p>In a hypothetical scenario, if you cut open a person's skull to show the live brain, and then you slowly start to crush it..</p>
<p>At what point would the person loose consciousness? </p>
<p>What would the person be feeling all this time?</p>
<p>Would it cause pain?</p>
| [
{
"answer_id": 10224,
"pm_score": 3,
"text": "<p>It depends on what part of the brain you are \"crushing.\"</p>\n\n<p>When we do brain surgery we often do exactly what you describe. That is, we open the skull and often remove part of the brain. However, in our case usually the part we are removing is di... | [
{
"answer_id": 9946,
"pm_score": 2,
"text": "<p>It seems there's way too many variables here. Crushing can occur in a number of ways, leading to different primary damage in different regions first and different people have a different level of system failure thresholds. </p>\n\n<p>Technically, there a... |
9,970 | <p>If a person positions him/herself upside down and swallows food, will it reach the stomach against gravity? If so how?</p>
| [
{
"answer_id": 9977,
"pm_score": 4,
"text": "<p>The eminent @JanDvorak has basically provided the full answer, but yes, it is possible. You can easily try this yourself, just lean off a bed and swallow something (small) and see what happens. <a href=\"https://en.wikipedia.org/wiki/Peristalsis\" rel=\"... | [
{
"answer_id": 69537,
"pm_score": 0,
"text": "<p>Yes it is possible. As I myself have experienced it.I was doing a headstand when I tried it.It does take a lot of time but does reach the stomach. </p>\n"
}
] |
9,989 | <p>A 5-year-old boy returns from summer camp with several minor cuts and abrasions on legs. He has fever
and extensive cellulitis, subcutaneous tissue and muscles are involved. Necrotic tissues were surgically
reomoved and broad spectrum antibiotics were used. Which of the following microorganisms usually
causes necrotizing fasciitis?</p>
<ul>
<li>a. bacillus cereus</li>
<li>b. clostridium tetani</li>
<li>c. A-group streptococci</li>
<li>d. Micrococcus sp.</li>
<li>e. Staphylococcus aureus</li>
</ul>
<p>It is so severe that I started think that Staphylococcus aureus is possible.
My previous answer was A-group streptococci, but I disagree with it now.</p>
<p><strong>What is causing the case?</strong></p>
| [
{
"answer_id": 9977,
"pm_score": 4,
"text": "<p>The eminent @JanDvorak has basically provided the full answer, but yes, it is possible. You can easily try this yourself, just lean off a bed and swallow something (small) and see what happens. <a href=\"https://en.wikipedia.org/wiki/Peristalsis\" rel=\"... | [
{
"answer_id": 69537,
"pm_score": 0,
"text": "<p>Yes it is possible. As I myself have experienced it.I was doing a headstand when I tried it.It does take a lot of time but does reach the stomach. </p>\n"
}
] |
10,002 | <p>I found a seemingly diseased tree when I was out playing tennis yesterday... What is growing on this tree leaf? Is this a disease? If so, is it contagious? I have zero knowledge in botany, but I'm curious about what is happening to these trees. :)
<img src="https://i.stack.imgur.com/LuHeQ.jpg" alt="enter image description here"></p>
| [
{
"answer_id": 42520,
"pm_score": 6,
"text": "<p>This is actually not a gall as <a href=\"https://biology.stackexchange.com/a/10004/16866\">other answers</a> have suggested.\nThis is likely a fungus called <strong>Cedar-apple rust (<em>Gymnosporangium juniperi-virginianae</em>)</strong>.</p>\n<p>The fun... | [
{
"answer_id": 10004,
"pm_score": 2,
"text": "<p>Briefly, these look like <a href=\"http://en.wikipedia.org/wiki/Gall\" rel=\"nofollow noreferrer\">insect galls</a>; which are reactions of plant tissue caused by parasitic insects (often wasps) laying eggs inside the leaf. I'm sure someone can answer in ... |
10,029 | <p>The mitochondria in the sperm are digested upon entry into the egg, making mDNA inheritance exclusively female. What is the advantage of this? Wouldn't some male mDNA be beneficial because of the advantages of (at least a little) sexual reproduction?</p>
<p>Reference:
"Postfertilization autophagy of sperm organelles prevents paternal mitochondrial DNA transmission" (behind paywall, <a href="http://www.sciencedaily.com/releases/2011/11/111103143515.htm" rel="nofollow">here's a ScienceDaily article discussing the results</a>).</p>
<p><strong>Edit:</strong></p>
<p>Both answers seem valid but it is hard to quantify the relative costs.</p>
| [
{
"answer_id": 10030,
"pm_score": 4,
"text": "<p>Maternal inheritance of mitochondrial DNA is very well conserved, although some species, such as <a href=\"https://www.ncbi.nlm.nih.gov/pubmed/11280005\">some mussels</a>, show <a href=\"https://en.wikipedia.org/wiki/Paternal_mtDNA_transmission\">paternal... | [
{
"answer_id": 51956,
"pm_score": 2,
"text": "<p>The mainstream theory, I believe, is that it's a way of avoiding the inevitable destructive (organismal fitness-lowering) competition that the two parents' mitochondria would otherwise be in.</p>\n\n<p>From Austin Burst and Robert Trivers' book <a href=\"... |
10,037 | <p>Is anyone aware of any attempts to count or approximate the number of trees there are in Sweden or Scandinavia? I have a small popular science side project for which this would be useful</p>
| [
{
"answer_id": 10071,
"pm_score": 2,
"text": "<p>I would definatley look at data from <a href=\"http://www.slu.se/riksskogstaxeringen\" rel=\"nofollow\">Swedish National Forest Inventory (Riksskogstaxeringen)</a>. They have time series data of multiple variables (DBH, size classes, species, dead wood et... | [
{
"answer_id": 10039,
"pm_score": 0,
"text": "<p>Did a bit of a search, but could not find any Scandinavian specific statistics; however, I did find <a href=\"http://epp.eurostat.ec.europa.eu/statistics_explained/index.php/Forestry_statistics\" rel=\"nofollow\">European Commission Forestry Statistics</a... |
10,056 | <p>Related to my earlier question, <a href="https://biology.stackexchange.com/questions/8857/how-does-the-human-liver-regrow">"How does the human liver regrow?"</a>, am curious as to why the liver is the only major organ that has this capability?</p>
<p>Why is it that other major organs, such as the heart and lungs etc are not able to regrow in the same fashion?</p>
| [
{
"answer_id": 10072,
"pm_score": 4,
"text": "<p>Maybe it is due to two factors:</p>\n\n<ol>\n<li><p>The liver is one of the few solid non-tubular organs. If a tubular organ is damaged, all the layers that composes it must regenerate. This layers usually have different cell types, which is always nasty ... | [
{
"answer_id": 73427,
"pm_score": 2,
"text": "<p>It helps to think about why it's beneficial for an organ/tissue to regenerate. The liver is your <a href=\"https://en.wikipedia.org/wiki/Drug_metabolism#Phases_of_detoxification\" rel=\"nofollow noreferrer\">main detoxifying organ</a>. It does this by che... |
10,060 | <p>From: <a href="http://www.nal.usda.gov/wicworks/Topics/FG/Chapter4_InfantFormulaFeeding.pdf" rel="nofollow">http://www.nal.usda.gov/wicworks/Topics/FG/Chapter4_InfantFormulaFeeding.pdf</a></p>
<blockquote>
<p>Discard any infant formula remaining after a feeding. The mixture of infant formula with saliva provides an ideal breeding ground for disease-causing micro-organisms.</p>
</blockquote>
<p>Why is this so? Doesn't Saliva contain anti-bacterial properties?</p>
| [
{
"answer_id": 10061,
"pm_score": 3,
"text": "<blockquote>\n <p>Doesn't Saliva contain anti-bacterial properties?</p>\n</blockquote>\n\n<p>Yes, in particular some IgA antibodies and lysozyme, but there are also plenty, and I mean <strong>plenty</strong> of bacteria in your mouth at any given point; we ... | [
{
"answer_id": 10083,
"pm_score": 0,
"text": "<p>Whether infant formula or food for adult consumption - should be discarded if there is salivary contamination since there is universal presence of microorganisms in saliva. These act as culture media and the microorgnisms rapidly degrade the food, not to ... |
10,082 | <p>Can the colour of skin change with age? Can a dark skinned person become fair or vice versa? Can Melanocyte production vary?</p>
| [
{
"answer_id": 10061,
"pm_score": 3,
"text": "<blockquote>\n <p>Doesn't Saliva contain anti-bacterial properties?</p>\n</blockquote>\n\n<p>Yes, in particular some IgA antibodies and lysozyme, but there are also plenty, and I mean <strong>plenty</strong> of bacteria in your mouth at any given point; we ... | [
{
"answer_id": 10083,
"pm_score": 0,
"text": "<p>Whether infant formula or food for adult consumption - should be discarded if there is salivary contamination since there is universal presence of microorganisms in saliva. These act as culture media and the microorgnisms rapidly degrade the food, not to ... |
10,090 | <p>As the question states, what are the limits of retroviral genetic delivery systems? </p>
<p>Are they limited to adding additional gene sequences to a cell, or can they actually overwrite specified segments of DNA?</p>
<p>Or, more aptly described, can they remove one segment of DNA, and insert a new segment (whether the same or different length) in the spot where the old segment used to be?</p>
| [
{
"answer_id": 10091,
"pm_score": 3,
"text": "<p>Retroviruses, such as HIV, have a genome that is composed of RNA. Once inside the host cell, that RNA is reverse-transcribed into DNA; it is that DNA which is <strong>inserted</strong> into the host genome. All retroviral genomes are integrated through ... | [
{
"answer_id": 10114,
"pm_score": 2,
"text": "<p>Just to give a simpler example of what Amory has explained. Viruses <em>can</em> overwrite existing information, just not the way you would think if coming from the world of computers.</p>\n\n<p>As already mentioned, viruses have the ability to insert the... |
10,176 | <p>I wonder if it matters if an average person eats the same amount of food distributed between a few (2-3) meals during the day, or constantly having small snacks.</p>
<p>I'm interested in several aspects of such food consumption:</p>
<ul>
<li>How does it affect appetite?</li>
<li>How does it affect fat accumulation?</li>
<li>Are there any notable side effects caused by either way of eating?</li>
</ul>
| [
{
"answer_id": 10181,
"pm_score": 3,
"text": "<p>1)Eating little with many breaks is healthy..\nEating rarely but many times increases your fat...\nThe logic is simple.</p>\n\n<p>Before the Logic..let me shoot a fact. \n<strong>In mammals: conversion from glucose to fatty acids has a direct pathway(I am... | [
{
"answer_id": 21622,
"pm_score": 2,
"text": "<p>Eating many small meals or eating large meals is irrelevant. The only thing that matters is getting the right amount of calories needed for your body to function properly.\nFat accumulation does not happen if you do not go over your daily calorie limit.\n... |
10,188 | <p>Lets say that the cell wants to make a particular protein. Transcription of the appropriate gene is done and the mRNA is made. mRNA attaches to the ribosome and the translation is initiated in a "normal" way. </p>
<p>What exactly would happen if an amino acid required in the protein is absent ? I know that the protein would not be manufactured properly but I want to exactly know what would happen to the ribosome and the mRNA. Are they destroyed? Are they simply separated? Who regulates this?</p>
| [
{
"answer_id": 10625,
"pm_score": 3,
"text": "<p><strong>It is not true that the anticodon of an uncharged tRNA can't bind to the mRNA.</strong></p>\n\n<p>Bacteria have a mechanism called <em><a href=\"http://en.wikipedia.org/wiki/Stringent_response\" rel=\"nofollow\">stringent response</a></em>. This r... | [
{
"answer_id": 10196,
"pm_score": 2,
"text": "<p><strong>Point to know : aminoacyl-tRNA binds to mRNA its not just t-RNA..</strong></p>\n\n<p>So if there is no Amino-acid there is no aminoacyl-tRNA of that aminoacid.. so if there is no aminoacyl-tRNA, the anticodon of tRNA doesn't form a bond with mRNA,... |
10,244 | <p>How many loci in the human genome are heterozygous? How about other species?</p>
<p>EDIT:<br>
I was wondering, considering for example the whole world population, how many of the human genes actually have two or more different alleles, or, vice versa, which genes everybody shares because there are no different versions of them. Since this seems not to be clear, I don't consider a mutation in a single individual an allele, maybe take 1% occurrence amongst all individuals as a start? I'm no biologist though...</p>
<p>By loci I mean whatever you think makes sense. Again, I don't mean single bases, preferably something like the classic idea of a gene. But I'm happy for whatever you can tell me.</p>
| [
{
"answer_id": 10257,
"pm_score": 3,
"text": "<p>If you want an actual number, well, it depends (of course). First off, what is your definition of loci? That term is broad, and can be construed to mean everything from large, megabase-length genes to every individual base.</p>\n\n<p>That being said, it... | [
{
"answer_id": 10253,
"pm_score": 0,
"text": "<p>The number of possible genotypes from only a few loci is great, and can be calculated using the formula </p>\n\n<p><strong>k(k+1)/2</strong></p>\n\n<p>where k is the number of alleles at a particular locus. </p>\n\n<p>The parameter k also represents the e... |
10,245 | <p><em>Clostridium tetani</em> (<em>C. tetani</em>) is a bacterium commonly found in soil and is excreted in the faeces of many animals (both mammals and birds) and serves, by means of the exotoxin, <em>tetanospasmin</em>, causes the life-threatening condition <strong>tetanus</strong>. </p>
| [
{
"answer_id": 10248,
"pm_score": 4,
"text": "<p>Soon after asking this question I found a reliable source, <em><a href=\"http://www.nlm.nih.gov/medlineplus/ency/article/000615.htm\">the National Institutes of Health</a></em>. It can survive for over 40 years.</p>\n"
}
] | [
{
"answer_id": 10247,
"pm_score": 2,
"text": "<p>Clostridia form endospores and can survive for years as a dormant spore. You can check this <a href=\"http://aem.asm.org/content/77/7/2352.full\" rel=\"nofollow\">article</a> about viability of clostridial endospores but it doesn't really talk about how l... |
10,284 | <p>Brain cells are cells require one of the highest amount of energy of any cell of body. So why do they use a shuttle which will transfer electrons from NADH produced in glycolysis to FAD(and there by reduce the no of ATP that can be made ) ? </p>
| [
{
"answer_id": 10438,
"pm_score": 3,
"text": "<p>In the absence of unanimous consensus and sources regarding the actual distribution of these shuttles,(wikipedia favours G3P shuttle abundance) let me try to explain the cause if the glycerol-phosphate shuttle is assumed to be prominent in brain cells. Se... | [
{
"answer_id": 93496,
"pm_score": 1,
"text": "<p>Looking at this question, which has resurfaced after five years, I was not really convinced by any of the possibilities suggested in the answer from @stochastic13, commendable attempt though it is. It happens that I have just been consulting the <a href=\... |
10,291 | <p>I know that metabolism as a whole can never be at equilibrium (otherwise the cell is dead !) but I wonder whether a few reactions in the cell could be at chemical equilibrium at a given point of time. </p>
<p>Is it possible theoretically ? Is there any real example ? </p>
| [
{
"answer_id": 10370,
"pm_score": 4,
"text": "<p>I think there are a few principles that we need to consider before answering your question.</p>\n<p>(a) When a reaction is at equilibrium, the rate of any elementary reaction is exactly balanced by that of the reverse process. This is an important one.</... | [
{
"answer_id": 10303,
"pm_score": 2,
"text": "<p>I am assuming that you know the difference between steady state and equilibria. Your definition of equilibrium is correct; fwd rate = bkwd rate.</p>\n\n<p>In a steady state the levels of a component remain constant over time but that may be because of man... |
10,322 | <p>Mitosis in eukaryotes happen in this order: DNA replicates and then the cell divides. Why doesn't it happen in reverse order (i.e., cell divides and then replicates the DNA)?
I am talking about diploid cells.
Why has evolution favoured the first way? </p>
| [
{
"answer_id": 10342,
"pm_score": 3,
"text": "<p>If you are thinking of a process like meiosis but followed by DNA duplication, the problem is that this would create daughter cells that do not have the same genome as the parent cell.</p>\n\n<p>The diploid genome of a sexually reproducing species' cell h... | [
{
"answer_id": 10327,
"pm_score": 1,
"text": "<p>The biggest problem is this: if you have only one copy of the DNA how is it going to divide it between the two cells so that both have a complete copy?</p>\n"
}
] |
10,329 | <p>Imagine we want to read impulses within single neurons in the brain. Can we do that now for a single region within the brain? If not, what is the smallest region that can be monitored for an activity in real time? Is there a more advanced method than electroencephalography for scaning brain activity in real time?</p>
| [
{
"answer_id": 20223,
"pm_score": 3,
"text": "<p>Electroencephalography has a good time resolution (milliseconds) but poor spatial resolution (several centimers). The usual estimated figure is that at least 50000 neurons need to fire simultaneously so that the activity can picked up by EEG.</p>\n\n<p>Th... | [
{
"answer_id": 10343,
"pm_score": 2,
"text": "<p>The smallest area that the EEG can measure is related to the electrode density. Even with research setups with 100s of electrodes, the smallest measurable region is on the order of a square centimeter or so on the skull surface. Brain regions deeper in th... |
10,373 | <p>Let's say I have a picture of an insect wing and a ruler on the same image. Is there any computer program that I can use to calibrate with the ruler and then get a measurement on the wing length? Would the software be able to export these data to a spreadsheet?</p>
| [
{
"answer_id": 10374,
"pm_score": 5,
"text": "<p><a href=\"http://rsbweb.nih.gov/ij/\">ImageJ</a> is all you need. Particularly see the documentation sections on <a href=\"http://rsbweb.nih.gov/ij/docs/guide/146-30.html#sub%3aSet-Scale...\">setting the image scale</a> and <a href=\"http://rsbweb.nih.gov... | [
{
"answer_id": 19292,
"pm_score": 1,
"text": "<p><a href=\"http://arohatgi.info/WebPlotDigitizer\" rel=\"nofollow\">WebPlotDigitizer</a> is an online application that can also be used to make distance and angle measurements in an image.</p>\n"
}
] |
10,402 | <p><strong>Why is it beneficial for trees to grow that tall?</strong></p>
<p>This sounds like a kid's question <code>Mom, Dad... why are trees so tall?</code></p>
<p><strong>Costs and Benefits</strong></p>
<p>There are some obvious costs:</p>
<ul>
<li>Need much Carbon and other nutrients</li>
<li>maintenance cost</li>
<li>energy cost (for growing, to bring water (and nutrients) up to the higher leaves, etc...)</li>
<li>Sensitivity to wind</li>
<li>etc...</li>
</ul>
<p>Potential benefits I can think of:</p>
<ul>
<li>Competition for sunlight</li>
<li>Better dispersal</li>
<li>protection against predation</li>
<li>Some birds (maybe especially those that are potentially good seed dispersers) prefer to land on high trees (avoiding the cost of regaining altitude). Being high attract these birds which eat the fruits and disperse the seeds. </li>
</ul>
<p><em>Are there other potential benefits?</em></p>
<p><strong>Specific to palm trees</strong></p>
<p>I am currently in Bali, Indonesia looking at palm trees that seem to have a very low competition for sun light (the forest is not dense, the light is intense), there are no tall predators (but being tall might be a protection against climbing predators as well and there are indeed monkeys and other potential climbing predators) and looking at coconuts, papaya and banana I can hardly think that being tall helps to disperse further away (seeds dispersal by <a href="http://en.wikipedia.org/wiki/Seed_dispersal_syndrome" rel="nofollow">barochory</a>). So, <strong>why (evolutionary reasons) are palm trees so high?</strong></p>
| [
{
"answer_id": 11041,
"pm_score": 3,
"text": "<p>Beside the reasons you've given I would add environmental disturbance (e.g. flooding) as a evolutionary factor that could explain selection for taller individuals. Many palms also inhabit and thrive in disturbed habitats (<a href=\"http://onlinelibrary.wi... | [
{
"answer_id": 10405,
"pm_score": 2,
"text": "<p>The height of tree species varies, of course, as each tree fills a given niche, much like animals do; you might as well ask why blue whales grow so big. The answer, of course, is that they seek out and successfully get the nutrients they require. It is ... |
10,429 | <p>I'm trying to be vegan, and purely natural foods lack sufficient calcium for the Recommended Daily Intake. Links 2 to 4 (but not 1) assert a correlation between calcium supplements and disease. </p>
<blockquote>
<p>[1. <a href="http://www.webmd.com/osteoporosis/features/calcium-supplements-pills?page=2" rel="nofollow noreferrer">WebMD</a> :] "Keep in mind that there's really not that much difference between getting calcium in a supplement and calcium in food."<br>
"Calcium-fortified foods -- such as cereals, some juices, and soy milk -- are excellent sources of the mineral, experts tell WebMD."</p>
<p>[2. <a href="http://www.health.harvard.edu/blog/high-calcium-intake-from-supplements-linked-to-heart-disease-in-men-201302065861" rel="nofollow noreferrer">health.harvard.edu</a> :] An 8-ounce portion of off-the-shelf orange juice contains about 300 mg of calcium. The calcium in fortified soy milk also compares favorably to whole milk.
Breakfast cereals (which are also fortified) contain substantial amounts of calcium, especially when combined with low-fat milk.
A portion of oatmeal on its own contains just 100 mg of calcium. “But if you cut up some dried figs and add it to a bowl of oatmeal with milk, you easily get about half of what you need without having any supplements,” Dr. Hauser says.</p>
<p>[3. <a href="http://well.blogs.nytimes.com/2013/04/08/thinking-twice-about-calcium-supplements-2/?_r=0" rel="nofollow noreferrer">NY Times Blog</a> :] All the researchers agree that, given the widespread use of supplemental calcium, better studies are needed to clarify possible risks and benefits, and to whom they may apply.</p>
<p>Until such information is available, consumers seeking to preserve their bones would be wise to rely primarily on dietary sources of the mineral and to pursue regular weight-bearing or strength-building exercises, or both. Walking, running, weight lifting and working out on resistance machines is unquestionably effective and safe for most adults, if done properly.</p>
<p>[4. <a href="http://www.nytimes.com/2011/01/25/health/25brody.html" rel="nofollow noreferrer">NY Times</a> :] The institute’s expert committee, which included bone specialists, concluded that most people don’t need supplements of these critical nutrients and warned of serious health risks from the high doses some now take — including <a href="http://health.nytimes.com/health/guides/disease/kidney-stones/overview.html?inline=nyt-classifier" rel="nofollow noreferrer">kidney stones</a> and heart disease linked to calcium supplements, and the very falls and fractures that vitamin D is meant to protect against.</p>
</blockquote>
<p><strong>5.</strong> How and why would the calcium carbonate from calcium supplements be asserted as worse than that in the fortified foods?</p>
<p><strong>6.</strong> Isn't solid calcium carbonate (e.g. in supplements) chemically the same as aqueous calcium carbonate (e.g. in fortified drinks)?</p>
<p><strong>7.</strong> Are calcium supplements really worse than fortified foods with calcium?</p>
| [
{
"answer_id": 10432,
"pm_score": 3,
"text": "<p>This is close to a personal medical question, so I'll try and be vague and avoid advice.</p>\n\n<p>There's nothing inherently <em>bad</em> about calcium supplements, and those links and thousands of others that are easy to find tend to all say that same t... | [
{
"answer_id": 49004,
"pm_score": -1,
"text": "<p>1 - probably because of regulation in the U.S. (and maybe other nations??). Nutrients added via fortification are regulated by the F.D.A essentially as foods. Nutrients in supplements are regulated essentially as manufactured goods. The difference -- d... |
10,436 | <p>Was there actually any useful knowledge gained from the Nazi experiments on human test subjects? Wikipedia cites freezing and phosphine gas reactions, but I would like to know other potential results from the Nazis.</p>
<p>At a first glance, it looks like the problem is that, in addition to the obvious ethical issues, there was also a lack if scientific rigor. Is this true or can some results actually be of some use?</p>
| [
{
"answer_id": 10439,
"pm_score": 5,
"text": "<p>Basically nothing. The Nazis did unfathomably terrible things of little value, and they did it poorly.</p>\n\n<p><a href=\"http://www.jlaw.com/Articles/NaziMedEx.html\" rel=\"nofollow\">This</a><sup>*</sup> is a fascinating, albeit long, read. It goes t... | [
{
"answer_id": 10461,
"pm_score": 3,
"text": "<p>This is an interesting question and one that really has two parts: the factual and the ethical. I remember discussing this topic in my 'ethics training' classes in graduate school (where I admit that I may have acted as an ass simply to demonstrate that o... |
10,446 | <p>Can hormones such as testosterone, aldosterone and estrogen cross the blood brain barrier?
I looked on Wikipedia and there no mention of it in the testosterone article. Through Googling around I also didn't find a list of which hormones can cross the barrier.</p>
| [
{
"answer_id": 10450,
"pm_score": 4,
"text": "<p>Yes, both steroid and peptidic hormones can enter the brain, the obvious proof being that the brain responds to changing blood concentration of hormones.</p>\n\n<p>The situation is different for steroid hormones (such as estrogen, testosterone, cortisol e... | [
{
"answer_id": 10451,
"pm_score": 2,
"text": "<p>Yeah indeed they can. The obvious proof is puberty and development, but a more involved look into how that is achieved can be found in <a href=\"http://endo.endojournals.org/content/153/9/4111.full.pdf\" rel=\"nofollow noreferrer\">this</a> free article ... |
10,466 | <p>A patient has a saline solution IV drip into the vein. They have somehow moved around and the needle has fallen out of the vein, but remained in the body. Nobody has noticed and for a few hours water has accumulated like a balloon in the arm.</p>
<p>What happens? Is it dangerous? If untreated, would the body absorb the water, or would it remain as a balloon / pocket? If a pocket of water forms, what is the treatment?</p>
| [
{
"answer_id": 10467,
"pm_score": 1,
"text": "<p><strong>CALL YOUR VET ASAP.</strong> The following information is <strong><em>NOT</em></strong> from a medical or veterinary professional. It is based off of human physiology and doesn't necessarily apply to other mammals. I cannot guarantee the accuracy ... | [
{
"answer_id": 31188,
"pm_score": 1,
"text": "<p>The most common IV drip that would be sent home with a pet owner is Ringer's solution. This fluid is also commonly injected as a subcutaneous (between muscle and skin) bolus into both cats and dogs. Although IV administration is more efficient, this fluid... |
10,493 | <p>Wikipedia says :</p>
<blockquote>
<p>The kidneys secrete a variety of hormones, including erythropoietin,
and the enzyme renin.</p>
</blockquote>
<p>Can a substance be both an enzyme and a hormone ? Why is renin both an enzyme and a hormone ?</p>
| [
{
"answer_id": 10496,
"pm_score": 4,
"text": "<p>Yes, something can be both a hormone and an enzyme. There are a group of hormones known as peptide hormones. These are proteins (such as enzymes) that act as hormones indirectly (and maybe directly too?). A hormone is a chemical secreted by a cell that ha... | [
{
"answer_id": 10510,
"pm_score": 1,
"text": "<p>Hormone is just a different class of protein and is not usually an enzyme. Peptide hormones have no catalytic potential and serve only as signaling ligands. </p>\n\n<p>There can be secreted enzymes which is common in the digestive tract but these are not ... |
10,497 | <p>I have searched the net and I have not been able to come up with an clear answer.</p>
<p><strong>Edit:</strong> Here is the para quoted from Nature <a href="http://www.nature.com/news/medical-research-cell-division-1.13273" rel="nofollow">http://www.nature.com/news/medical-research-cell-division-1.13273</a>
<strong>"So began WI-38, a strain of cells that has arguably helped to save more lives than any other created by researchers. Many of the experimental cell lines available at that time, such as the famous HeLa line, had been grown from cancers or were otherwise genetically abnormal. *<em>WI-38 cells became the first 'normal' human cells available</strong> in virtually unlimited quantities to scientists and to industry and, as a result, have become the most extensively described and studied normal human cells available to this day".</em>*</p>
| [
{
"answer_id": 10501,
"pm_score": 4,
"text": "<p>The answer is that the majority of the cells were frozen from very early in their Hayflick lifetimes e.g. after 9 population doublings. They have been thawed out judiciously and only as needed thus preserving a lot of frozen stocks. When an ampule of cel... | [
{
"answer_id": 10502,
"pm_score": 0,
"text": "<p><a href=\"http://en.wikipedia.org/wiki/WI-38#History\" rel=\"nofollow\">WI-38 are the cell lines which led to the proposal of the Hayflick limit</a> and are the classic example of cells which will only divide ~40 times. they are not exempt - they are the... |
10,544 | <p><a href="http://www.scientificamerican.com/article.cfm?id=identical-twins-genes-are-not-identical" rel="nofollow">http://www.scientificamerican.com/article.cfm?id=identical-twins-genes-are-not-identical</a></p>
<p>According to this article some identical twins show differences with respect to their copy number variants. How is this possible? If mitosis of an egg can lead to this difference, why can't mitosis of any cell in our body?</p>
<p>If we assume that identical twins are exactly identical, then if we make a clone of a twin will all three be exactly identical?</p>
| [
{
"answer_id": 10545,
"pm_score": 4,
"text": "<p>Errors in division occur all the time and can show up in any dividing cell; this is, of course, important for cancer biology. If one of my cells replicates oddly right now it likely won't matter since it's only one out of trillions, but if that happened ... | [
{
"answer_id": 10546,
"pm_score": 2,
"text": "<p>Identical twins do start out identical, but their DNA will quickly diverge. Not in a dramatic way, but in point mutations, at random locations, in different cells. Think of how there is a certain error rate associated with DNA replication - so even from ... |
10,692 | <p>I am reading a paper which discusses Maize Genome Structure. Descriptions of the structure is given in the papers introduction.
I know about heterochromatin "heterochromatin stains intensely, indicating tighter packing. Heterochromatin is usually localized to the periphery of the nucleus"
but, could someone explain what is knob heterochromatin? </p>
<p>thanks for help.</p>
| [
{
"answer_id": 10701,
"pm_score": 2,
"text": "<p><a href=\"http://mnl.maizegdb.org/mnl/61/133eubanks.html\" rel=\"nofollow noreferrer\">Here's a good summary of knobs</a>, which says that they are "<em>typically telomeric</em>," "<em>tandemly repeated DNA sequences [that] appear as distin... | [
{
"answer_id": 10693,
"pm_score": 0,
"text": "<p>I found it in <a href=\"http://www.nature.com/nrg/journal/v9/n6/glossary/nrg2341.html\" rel=\"nofollow\">this article</a> :</p>\n\n<blockquote>\n <p>Heterochromatic knob\n A chromosomal region that can \n be identified microscopically as \n being dark... |
10,707 | <p>I'm a first year student and I'm not sure if I understand correctly the role played by the antibiotic 'kanamycin' in the growing of culture E. coli (Rosetta).</p>
<p>Can anybody explain me why we use 'kanamycin' antibiotic and kanamycin resistance gene during that process?</p>
| [
{
"answer_id": 10709,
"pm_score": 2,
"text": "<p>Absolutely, <strong>Positive Selection</strong></p>\n\n<p>You are looking for the bacteria which <em>have</em> the gene (probably a plasmid) you (or someone else for you) put into the bacteria. That gene lets them live in the presence of kanamycin, and a... | [
{
"answer_id": 10735,
"pm_score": 2,
"text": "<p>According to <a href=\"http://www.emdmillipore.com/is-bin/INTERSHOP.enfinity/WFS/Merck-US-Site/en_CA/-/USD/ViewPDF-Print.pdf;sid=IusRzR8X54wRzU1GAnZ9mrfXpWgDPXWwGsUPm6y6AJ-vrpGZDgtyZxkpNbCccDRuopgB0RzO39M4ypbegG-kJrBdAx8IidPHEXGp7KcOcrrlQ6r8jaGYBL2T?Rende... |
10,779 | <p>Cushing's syndrome results from increased levels of cortisol in the body.</p>
<p>Cortisol as I understand it however, promotes the breakdown of glycogen and amino-acids in the process of gluconeogenesis, to increase blood sugar - opposing the action of insulin.</p>
<p>Why then does Cushing's syndrome lead to weight gain rather than weight loss?</p>
| [
{
"answer_id": 10780,
"pm_score": 3,
"text": "<p>Cortisol is released when body goes through stress situations like while working out in gym, physiological activities outdoor etc. As you have already mentioned about what Cortisol does, it accumulates in the body after the stress situation and then with ... | [
{
"answer_id": 39414,
"pm_score": 0,
"text": "<p>I read this somewhere. In Cushing's syndrome the excessive cortisol disables metabolism of proteins and fats rather than increasing it ( I don't know the reason). Hence, fat gets accumulated, mainly in the abdominal region resulting in weight gain</p>\n"
... |
10,791 | <p>Is it possible to determine if a certain specific mutation had a spontaneous origin (for example from a mistake of the DNA polymerase) as opposed to an induced origin (for example, from some genotoxic agent)?</p>
| [
{
"answer_id": 10800,
"pm_score": 3,
"text": "<p>Here's a quick answer; hopefully someone will give a more complete one. But meanwhile you've got something. </p>\n\n<p>Some genotoxic agents have predictable results. For example, they cause Gs to substitute for Cs, or they cause mutations at specific ... | [
{
"answer_id": 11023,
"pm_score": 0,
"text": "<p>The above answer is mostly right. In the lab one can show that induced mutations are caused by exposure, compared to unexposed controls (e.g. in bacteria). The induced mutations will have a frequency, position, and type which can be typified. As a group, ... |
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