qid int64 2 112k | question stringlengths 61 6.7k | positives listlengths 1 1 | negatives listlengths 1 10 |
|---|---|---|---|
111,514 | <p>Humans can tolerate a <a href="https://space.stackexchange.com/questions/32640/what-is-the-maximum-atmospheric-pressure-a-human-can-tolerate#:%7E:text=NCBI%20provides%20a%20short%20paper,would%20be%20100atm%20of%20pressure.">maximum pressure of 100atm, but it becomes uncomfortable above 30 atms</a>. Deep divers usually wear protective equipment like goggles among other things and our eyes seem to be <a href="https://kidshealth.org/en/teens/eyes.html#:%7E:text=All%20parts%20of%20the%20eye,it%20is%20surrounded%20by%20bone." rel="nofollow noreferrer">more fragile</a> than the rest of our body.</p>
<p>So, <strong>without using goggles how deep can a human open their eyes under water before suffering from an injury?</strong></p>
<p>The injury, I believe, would be the eye getting crushed by external pressure.</p>
| [
{
"answer_id": 111515,
"pm_score": 5,
"text": "<p>Crushing damage from pressure occurs due to pressure <em>differences</em>. Imagine you have a rigid container. If you have equal gas pressure inside and outside, the pressure acts on just the walls and the container will survive unless the pressure is hi... | [
{
"answer_id": 111516,
"pm_score": 3,
"text": "<p>Currently the record for the deepest dive wearing scuba equipment is 332.35m. The descent took only 15 minutes while the ascent lasted 13 hours 35 minutes.</p>\n<p>Liquids do not compress, so the sinuses, inner ear, lungs and circulation are in far more ... |
16 | <p>Has anyone tried the chew back-anneal in vitro DNA assembly method (known as Gibson Assembly) for difficult sequences, like GC-rich sequences? How big constructs could you efficiently assemble? Did you use the original protocol or some optimizations?</p>
| [
{
"answer_id": 42,
"pm_score": 4,
"text": "<p>I haven't tried Gibson Assembly myself, but I do know the <a href=\"http://2011.igem.org/Team%3aCambridge/Project/Gibthon#/Project/Gibthon\">Cambridge iGEM Team in 2010 and 2011</a> developed a web-based tool - <a href=\"http://www.gibthon.org/\">Gibthon</a>... | [
{
"answer_id": 1107,
"pm_score": 2,
"text": "<p>I also haven't tried it, but theoretically GC-rich sequences will interfere with Gibson assembly. Since unique homology between the ends is key to the assembly process, repetitive sequences which cause non-unique overhangs will increase the possibility of ... |
27 | <p>We know from pop science that our psychological states have an effect on our immune systems ("worrying ourselves sick", etc.), but what are the actual mechanisms through which our nervous systems pass information to the immune system?</p>
<p>Cell mediators come to mind, but where in the body would a nerve cell release an interleukin or other factor? (Put another way, are neurons releasing these factors as a part of their normal cell metabolism and the side effect is a communicative effect with the immune system?)</p>
| [
{
"answer_id": 39,
"pm_score": 5,
"text": "<p>It is not only the immune system that prevents us from getting ill. Worrying much in my opinion won't make you catch a cold; rather, you can get problems with your cardiovascular system (arrhythmias, hypertension, angina pectoris) or limbic system (panic att... | [
{
"answer_id": 48343,
"pm_score": 1,
"text": "<p>Here's pretty much the first thing that popped up on pubmed:<a href=\"http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3144148/\" rel=\"nofollow\">http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3144148/</a>\n So clearly there are direct neurotransmitter receptors... |
64 | <p>What is the current consensus on whether or not humans have receptors that detect pheromones?</p>
<p>If there are purported receptors, in what anatomical areas are they located? With what organ systems do they interact? </p>
| [
{
"answer_id": 68,
"pm_score": 4,
"text": "<p>From what I have gathered, I would think that humans do have receptors that are able to detect pheromones.</p>\n\n<p>For example, some studies that have indicated human responses to pheromones. Of these pheromone responses, some have been traced to the olfa... | [
{
"answer_id": 155,
"pm_score": 3,
"text": "<p>Well... I'm excited that my first contribution to this site will include a study of strippers!</p>\n\n<p><a href=\"http://whywereason.wordpress.com/2011/06/29/menstruation-attraction-why-females-shouldnt-flirt-while-menstruating-and-why-bears-can-smell-the-... |
69 | <p>I understand that rooted and unrooted phylogenetic trees are similar in structure</p>
<p>But how can they be easily identified as one or the other?</p>
<p>Is it simply based on the presence or lack of a named root (the root is identified as a particular ancestor) or outgroup?</p>
| [
{
"answer_id": 74,
"pm_score": 4,
"text": "<p>In case of a drawn figure, either look for the a short stem to the left, or for an explicitly labelled outgroup. Trees derived from phylogenetic analyses are normally unrooted by default, you need to root them by either making an arbitrary (but hopefully inf... | [
{
"answer_id": 71,
"pm_score": 2,
"text": "<p>Trees can not be distinguished from each other because every unrooted tree can be made rooted by adding a root and vice versa by deletion.</p>\n\n<p>If you mean dendrograms... the root is always the one node where the distance to each leaf is the same. But I... |
72 | <p>For predicting genes from a sequenced genome, you need to set a maximum intron length. How long can introns get in animals? Is there some limit?</p>
| [
{
"answer_id": 294,
"pm_score": 4,
"text": "<p>I think the above values (500-750 kb) are wrong. <a href=\"http://www.bioinfo.de/isb/2004040032/\">http://www.bioinfo.de/isb/2004040032/</a> shows that most introns are less than about 10 kb (and personal experience in Drosophila confirms that - I've <em>r... | [
{
"answer_id": 153,
"pm_score": 3,
"text": "<p>If you examine the human genome ~99% of the introns are under 500 kb. I would assume that a limit between 250 kb - 500 kb is reasonable for gene prediction. You may incorrectly predict the proper structure of a small number of genes that have these very la... |
82 | <p>Once upon a time, I chanced upon an old microbiology book that detailed the rather colorful world of enterobacteria. <em>Salmonella</em> in particular stood out, as it seemed there were a lot of species: <em>typhi</em> / <em>typhosa</em>, <em>paratyphi</em>, <em>gallinarum</em>, <em>typhimurium</em>, <em>choleraesuis</em>, and quite a bunch of others that I have now forgotten.</p>
<p>Flipping through a newer book, it now seems that all of these "species" were collated under <em>choleraesuis</em> (and now more recently <em>enterica</em>), with all those species being demoted to "strains" (or maybe I should use the current term of art, "serovar"). Unfortunately, the book didn't give much in the way of explaining about this merger.</p>
<p>So, why is there now only <em>S. enterica</em>? If "<em>S. typhi</em>" is a mere serovar, how come the species name is still used in the literature?</p>
| [
{
"answer_id": 88,
"pm_score": 5,
"text": "<p>Simply put, old habits die hard; physicians and other medical personnel have grown up with the old species designations so will continue to use them. This is somewhat the reverse of the case with <em>E. coli</em>, where <a href=\"http://www.ncbi.nlm.nih.gov... | [
{
"answer_id": 85,
"pm_score": 2,
"text": "<p>Just open Wikipedia, your question is <a href=\"http://en.wikipedia.org/wiki/Salmonella#Salmonella_nomenclature\" rel=\"nofollow\">answered there</a>:</p>\n\n<blockquote>\n <p>Initially, each Salmonella species was named according to clinical\n considerati... |
91 | <p>The information between the brain and peripheral nerves is sent via electrical pulses or signals, How then does a non-metallic human cell manage to conduct an electrical
signal?</p>
| [
{
"answer_id": 110,
"pm_score": 6,
"text": "<p>This is quite a big question! I'll try to outline the basic view.</p>\n\n<p>First, let's review how neurons signal between each other. The canonical way for a neuron to send a signal to a downstream neuron is by generating an <strong>action potential</stron... | [
{
"answer_id": 104,
"pm_score": 4,
"text": "<p>So, let us introduce some keywords.</p>\n\n<p>The \"electrical pulse\" that \"is sent from between brain and nerves\" is called an <strong>Action Potential</strong> (AP). This is then <strong>propagated</strong> along a nerve fiber until the target organ.</... |
92 | <p>It was somewhat new to me that mushrooms usually aren't individual organisms, but are merely the visible bodies of a bunch of fungi living in the soil. I know that mushrooms emit spores to reproduce, but what has been bizarre to me is how fairy rings form. Why do the fruiting bodies arrange themselves in a more or less circular shape, as opposed to the random scattering one would expect from wind-borne spores?</p>
| [
{
"answer_id": 97,
"pm_score": 5,
"text": "<p>When a fungal spore germinates in a suitable location, the growing mycelium will spread underground in all directions. In the ideal situation, the result is that the mycelium will become circular. Over time, the center of the mycelium will die out whereas th... | [
{
"answer_id": 103,
"pm_score": 4,
"text": "<p>In addition, the mycelia (the underground mass of hyphae which constitutes the bulk of the fungus) expand <strong>outwards</strong> because they decompose organic matter in soil as they go, leaving very little organic matter in the soil in the interior of t... |
107 | <p>While investigating the rise of adult lactose tolerance, I came across the news that China has been encouraging its citizens to drink more milk, even though most of the Asian population lacks the SNP (single-nucleotide polymorphism) which conveys lactase persistence.</p>
<p>Is it still possible for an adult without lactase persistence to build-up a tolerance for lactose over time? If so, what's the mechanism?</p>
| [
{
"answer_id": 161,
"pm_score": 5,
"text": "<p>It seems that yes, it is possible to increase the tolerance for lactose over time, and it has to do with the adaptation of microbiota.</p>\n\n<p>A simplistic explanation comes in the following article: \n<a href=\"http://www.ncbi.nlm.nih.gov/pubmed/8694025\... | [
{
"answer_id": 123,
"pm_score": 3,
"text": "<p>Here are my thoughts on the topic.</p>\n\n<p>Dairy good is not only milk, but also the following milk products: sour milk products (like yougurt, kefir, katik, buttermilk, etc.), cheese, etc. These products can contain less lactose than in the milk solids (... |
121 | <p>I'm looking for a protocol to get genomic DNA from an <em>E. coli</em> sample so that I can clone a small portion of it using PCR into a plasmid. (< 500 bp in this case). </p>
<p>It seems <a href="http://openwetware.org/" rel="nofollow">OWW</a> (Open Wet Ware) only discusses preparation of fragmented DNA. Does this mean I have to cut it up before I can clone from it? Any pointers would be really appreciated.</p>
| [
{
"answer_id": 1150,
"pm_score": 1,
"text": "<p>Hey all I think I didn't know how to word this question properly. After asking a colleague I was told that I don't need to prepare the DNA at all for this tiny non-library scenario. </p>\n\n<p>She told me to just take a little smear of bacteria on a tooth... | [
{
"answer_id": 184,
"pm_score": 3,
"text": "<p>Yes, you must fragment the genome in order to insert it into a vector for cloning; you can't \"insert\" the whole 5 Mbp genome of <em>E. coli</em> into a vector. It's difficult to transform cells with huge plasmids, 2-20 kbp is an optimal range. In any ca... |
126 | <p>The pig is only an example, just an animal. Leydig cells have protein inclusions (Reinke crystals) that are mostly made of crystallised lipofuscin. They are secretory inclusions i.e. cells formed in secreting cells.</p>
<p>An example of Leydig cell in pig's testicle:</p>
<p><img src="https://i.stack.imgur.com/IJ3Hq.jpg" alt="enter image description here"></p>
<p>My teacher told me that there is a difference in the existence of some cells between humans and animals.
However, I cannot find such a difference. I have not been provided a slide of human Leydig cell so I have not been able to compare.</p>
<p><strong>What is the morphological difference between Leydig cell in human and pig?</strong> </p>
| [
{
"answer_id": 648,
"pm_score": 4,
"text": "<p>Perhaps what your teacher meant was not so much a difference in Leydig cell morphology, but in <strong>interstitial tissue morphology</strong>, ie. tissue which occupies the space in between seminiferous tubules. Leydig cells are its most interesting compon... | [
{
"answer_id": 638,
"pm_score": 3,
"text": "<p>I have studied all available (via University library) literature on the Leydig cells and I think your teacher might have <a href=\"http://joe.endocrinology-journals.org/content/168/2/213.full.pdf\" rel=\"nofollow noreferrer\">this article</a> summarizing th... |
163 | <p>Much interest in the astrobiology community has been generated by the discovery of biological communities populating deep-ocean hydrothermal vents (i.e. "black smokers"). (1) These ecosystems rely on chemoautotrophic bacteria/archaea extremophiles as primary producers living at 40-80 C temperatures. </p>
<p>However, the lifetimes of these black smokers have been estimated to be of order 25 years. How are these biological communities able to migrate to newer, active vent systems in conditions of extreme cold and high pressure?</p>
<p><a href="http://www.sciencedirect.com/science/article/pii/0146629177904787">(1) Lonsdale, P., 1977, Deep Sea Research, 24, 9</a></p>
| [
{
"answer_id": 292,
"pm_score": 5,
"text": "<p>I did some research on the topic and came accross <a href=\"http://www.cryoung.org/www/pdfs/Johnson_et_al_biobull.pdf\">this paper</a> by Johnson <em>et al</em>. I am not a zoologist, so everything I write here is taken from the references paper.</p>\n\n<p>... | [
{
"answer_id": 374,
"pm_score": 4,
"text": "<p>Following up on Alexander's response, I read a little more on the subject by looking at some of the references in the Johnson et al. paper.</p>\n\n<p><a href=\"http://www.pnas.org/content/107/17/7829.full\" rel=\"noreferrer\">This paper</a> discusses an in... |
165 | <p>This is an assignment that had confused me for a long time. So I think you guys who study computational biology might be interested. The original question is:</p>
<blockquote>
<p>Find the two most similar DNA sequences of length 20 that Blast using a word length of 5 will fail to align.</p>
</blockquote>
| [
{
"answer_id": 167,
"pm_score": 5,
"text": "<p>BLAST works by finding a perfect match between sequences of a length equal to this \"word length\" and then enlarging it in a standard way -- yet there will be no alignment without this perfectly matched word.</p>\n\n<p>So in your case, you must look for tw... | [
{
"answer_id": 3840,
"pm_score": -1,
"text": "<p>I am not sure I understand BLAST correctly. </p>\n\n<p>When using BLAST in DNA and protein, they are different. There is a threshold T in protein \"seeding\" step, which means the seeding sequence is not perfectly matched. However, it seems there is no T ... |
178 | <p>I've gotten a staggering amount of use out of my copy of <em>Fields Virology</em> as a general reference for "getting me up to speed" on whatever pathogen I'm currently looking at. I don't know of a similar type of reference for bacteria, but I only became aware of <em>Fields</em> as I was moving <em>out</em> of the field, rather than into it, so it's possible I've simply never heard of a suitable reference.</p>
<p>Any suggestions?</p>
| [
{
"answer_id": 181,
"pm_score": 4,
"text": "<p>I might as well give this as an answer: the closest analog to Fields for bacteriology that I'm aware of are the two Bergey's manuals: <a href=\"http://www.springer.com/series/4157\"><em>Bergey's Manual of Systematic Bacteriology</em></a>, and <a href=\"http... | [
{
"answer_id": 269,
"pm_score": 3,
"text": "<p>The Manual of Clinical Microbiology from ASM is the bible we use in our Micro lab. It's often our first reference. There are a lot of other useful books in the ASM eStore. </p>\n\n<p><a href=\"http://estore.asm.org/viewItemDetails.asp?ItemID=1021\">ASM eSto... |
182 | <p>In the sinusoids of the liver, venous blood from the hepatic portal system mixes with arterial blood from the hepatic arteries. </p>
<p>Do oxygen molecules move between oxygenated RBCs and non-oxygenated RBCs, so that the partial oxygen saturation of the blood in the sinusoids reflect partial saturation of the RBCs? Or do RBCs retain their initial oxygen saturation, so that the partial saturation of the blood in the sinusoids reflects a mixture of saturated and unsaturated RBCs?</p>
| [
{
"answer_id": 422,
"pm_score": 4,
"text": "<p>The <strong>oxygen saturation</strong> (in lungs) and desaturation (in target organs) <strong>takes place via diffusion</strong> along the concentration gradient (i.e. partial pressure for gases). Therefore as long as <strong>RBCs</strong> from two differen... | [
{
"answer_id": 76420,
"pm_score": 2,
"text": "<p>I'm not aware of any studies that investigate the equilibration of oxygen saturation between two individual cells in hepatic sinusoids, but I will answer based on what we know about these issues in the general context.</p>\n\n<p>See West, Pulmonary Pathop... |
183 | <p>Commercial suppliers of primary antibodies for given protein targets typically list recommended applications, for which the antibody has presumably been shown to work. I am usually looking to use them for immunofluorescence, and my impression (which admittedly may be based on an unrepresentative sample) is that most antibodies are recommended only for use with Western Blotting.</p>
<p>Why is this? Is WB the most common application? The most general? Is it easier to test for than IF?</p>
<p>And, perhaps more to the point, how seriously should one take these recommendations? If an antibody is not recommended for IF, does that mean that it probably won't work? Or that it may well but no-one's bothered to check? Or that it almost certainly will?</p>
| [
{
"answer_id": 191,
"pm_score": 4,
"text": "<p>Maybe WB is easier for them to test?</p>\n\n<p>In general, however, my recommendation is to check if they provide refs to paper using those antibodies and look at the images on the paper.</p>\n\n<p>Be careful putting your trust in the supplier's pictures, I... | [
{
"answer_id": 278,
"pm_score": 2,
"text": "<p>Antibodies for WB and for IF have fundamentally different requirements for the epitope structure. Antibodies for WB recognize denatured structures extended by SDS treatment. Antibodies for IF often will need to recognize a native-like structure. </p>\n\n<p>... |
186 | <p>Several companies are commercializing tests for telomere length such as this one <a href="http://www.telomehealth.com/index.html">here</a>. I understand the basic mechanism for why telomeres shorten during DNA replication, but how good is the evidence that telomere length is a reliable indicator of healthspan/lifespan?</p>
| [
{
"answer_id": 331,
"pm_score": 5,
"text": "<p>I disagree with Ctina. So many factors go into determining loss rate, activity of telomerase, gene conversion or unequal exchange at chromosome ends, etc to ever say that length is a function of age. There is far more variation between individuals and bet... | [
{
"answer_id": 2766,
"pm_score": 2,
"text": "<p>A number of studies have compared replicative capacity of cells with lifespan. Since Replicative capacity of cells is linked to telomere-length, these studies may provide indirect evidence for the association between telomere length and lifespan. One int... |
190 | <p>What are the major evolutionary pressures for Bioluminescence?</p>
| [
{
"answer_id": 194,
"pm_score": 5,
"text": "<p>In many cases, and in particular in marine invertebrates, the bioluminescence is in fact produced by symbiotic bacteria of the Vibrionaceae family. In most cases the bacteria can sense when they are being hosted by the animal through quorum sensing mechanis... | [
{
"answer_id": 196,
"pm_score": 3,
"text": "<p>Bioluminescence, in particular in marine organisms, has also been linked to way to get rid of reactive oxygen species (ROS). In fact, luciferases catalyse the photogenic oxydation of luciferins. In [<a href=\"http://jeb.biologists.org/content/201/8/1211.ful... |
195 | <p>When cold or in shock a person's blood vessels constrict in order to preserve heat or to move blood flow to protect vital organs. I am interested in the mechanism by which this is achieved. Does this occur along the entire length of the limb or are there 'pinch points' (for example is it possible to simply have a point of vasoconstriction just below the shoulder which would reduce blood flow to the entire arm)? Am I correct in thinking that the response is neurological rather than endocrinological ?</p>
| [
{
"answer_id": 213,
"pm_score": 3,
"text": "<p>Reduced blood flow to a region of the body occurs through 2 principal mechanisms.</p>\n\n<p>1) The smooth muscle fibers in the tunica media layer of the arteries contract and reduce the diameter of the artery, limiting blood flow due to increased resistance... | [
{
"answer_id": 198,
"pm_score": 3,
"text": "<p>Vasoconstriction is a phenomenon that can be caused by many factors, from mechanical events (such as stretching) to hormones (epinephrin, neurepinephrin, angiotensin ...). But no matter what is the cause, the end-result is an increase in intracellular calci... |
230 | <p>Vaccines, especially those given in adulthood, usually have term limits attached, eg: 10 years for yellow fever or 3 years for typhoid. Since presumably the time course of an immune response is no great respecter of our calendrical conventions, and since there is also presumably a spectrum of responses across the population, how are these durations estimated? What are the criteria for deciding a cutoff time?</p>
<p>Also, do the estimates get revisited and updated as time goes on and new data become available? <em>Do</em> new data become available? Is there continuing follow-up research into this, or does the estimate just get made before the vaccine comes to market and then get taken as gospel?</p>
| [
{
"answer_id": 244,
"pm_score": 5,
"text": "<p>Duration of efficacy is typically determined by tracking the antibody titers of a cohort of subjects who have gotten the vaccine, and estimating based on the trajectory of those titers where they will eventually cross the threshold to the point where the va... | [
{
"answer_id": 3559,
"pm_score": 0,
"text": "<p>I read somewhere (I don't have a citation) that duration of efficacy is limited by the evolution of viral antigens; eventually the population will evolve to the point where the immune system no longer recognizes them effectively. RNA viruses have more vola... |
239 | <p>Darwin suggested that sexual selection, especially by female choice, may counter natural selection. Theoretical models, such as a Fisherian runaway process, suggest that evolution of preference and preferred phenotypes may drive each other in ever increasing speed. </p>
<p>Because one male may fertilize many females, one could imagine that natural selection against preferred but energetically costly phenotypes may be weak, and the whole process may not slow down fast enough (i.e., be sufficiently self-limiting). If male mortality is high and their number is low, the random fluctuations may easily cause the extinction of population.</p>
<p>Is there any fossil or experimental evidence that this may really happen?</p>
| [
{
"answer_id": 254,
"pm_score": 7,
"text": "<p><strong>TL;DR</strong>: </p>\n\n<ul>\n<li><p>There is a dearth of actual experimental evidence. However:</p>\n\n<ul>\n<li><p><strong>there is at least one study that confirmed the process</strong> ([<strong>STUDY #7</strong>] - Myxococcus xanthus; by Fiegna... | [
{
"answer_id": 8665,
"pm_score": 3,
"text": "<p>Relating to your last comment on random fluctuations in survival, a recent theoretical paper by <a href=\"http://www.jstor.org/stable/10.1086/658344\">Lee et al. 2011</a> studies the effect of mating systems on demographic stochasticity in small population... |
295 | <p>I got the question in my exam and wrote the following and I do not understand what is wrong in it:</p>
<blockquote>
<p>Giemsa staining is a staining method to stain particularly malaria and other parasital diseases. G-bands occur because Giemsa stain
consists of A,T rich material i.e. poor gene such that dark and white
bands occur. Each chromosome has an unique reaction to Giemsa staining
so G-bands occur.</p>
</blockquote>
<p>0 points. I do not understand what's wrong with it, since in their comments about the same question in my first exam they wrote also the extra questions: <strong>What are G-bands? How are they formed and why?</strong> This time I answered the given things and got zero mark.</p>
<p>Probably, the mistake was that I did not answer to the question in the scope of medical Biology in some way. However, I am not exactly sure what it is exactly.</p>
<p><strong>How would you answer to the question when you know that the course was about medical biology?</strong></p>
<p>Please, add the tag Giemsa.</p>
| [
{
"answer_id": 301,
"pm_score": 3,
"text": "<p>Giemsa is not a particular methid to stain malaria or any other parasite. It stains DNA. As such, it can be used to stain any DNA-containing organism, or, in other words, any known cell.</p>\n<p>Regarding its particular use in chromosomal banding, you can r... | [
{
"answer_id": 297,
"pm_score": 1,
"text": "<p>Probably they want something like from <a href=\"http://www.google.fi/url?sa=t&rct=j&q=giemsa%20staining%20filetype%3appt&source=web&cd=1&ved=0CBwQFjAA&url=http://wwwu.tsgh.ndmctsgh.edu.tw/cp/%25E8%258B%25B1%25E6%2596%2587%25E7%25B6%... |
305 | <p>What is the smallest viable reproducing population, such as in a human population. By viable I mean a population which keeps genetic defects low (enough).</p>
<p>A very strongly related question: what is the expected number of generations a given population can survive?</p>
| [
{
"answer_id": 311,
"pm_score": 6,
"text": "<p>The conservation biology literature has a great deal of information, particularly with reference to developing species survival plans (e.g., <a href=\"http://www.sciencedirect.com/science/article/pii/S0006320707002534\">Traill et al. [2007]</a> report a min... | [
{
"answer_id": 317,
"pm_score": 2,
"text": "<p>I suspect the answer would definitely include a parameter that would state how 'diverse' the reproducing population is to begin with - including how heterozygous each individual is (versus inbred); as well as across individuals - i.e. how different these ... |
315 | <p>We all know restriction enzymes are proteins, but we never freeze them. They are instead provided in high glycerol containing solutions by companies and stored at -20C. Is there a reason why this is so?</p>
| [
{
"answer_id": 316,
"pm_score": 5,
"text": "<p>It's just so much more convenient to have the enzymes ready without having to thaw them. The main reason you freeze enzymes is to keep them active, if you figure out a buffer that keeps them unfrozen without compromising activity, that is a huge increase in... | [
{
"answer_id": 327,
"pm_score": 3,
"text": "<p>Freeze-thaw cycles denature proteins through local pH change effects</p>\n"
}
] |
320 | <p>My teachers growing up told me it was impossible to decode the maize genome. But yet its been done. </p>
<p>Why was decoding the genome so significant, and what made it so difficult?</p>
| [
{
"answer_id": 322,
"pm_score": 6,
"text": "<p>The short answer is that corn genome is large and has a huge amount of duplication events. Around 80% of the genome are repeated. It's hard to assemble genomes with large amount of duplications because our sequencing technology, practically, at best can giv... | [
{
"answer_id": 507,
"pm_score": 3,
"text": "<p><strong>Why was decoding the genome so significant?</strong>\nBecause decoding the genome gives us a complete picture of the genetic makeup of an organism.</p>\n\n<p><strong>What made it so difficult?</strong>\nThe repetitive sequences as mentioned by other... |
339 | <p>I'm a biology amateur, but it seems like sexual selection is almost always performed based on physical characteristics, the outcome of physical contests, or some sort elaborate courtship. But do any non Homo-Sapiens perform sexual selection based on intelligence factors, like problem solving abilities? If so, how does the species accomplish this? I know natural selection as a whole would definitely favor intelligent individuals, but I'm curious if any species actually takes this into account when choosing mates. </p>
| [
{
"answer_id": 342,
"pm_score": 6,
"text": "<p>Very intresting question. The problem is that animal intelligence is hard to measure not only for scientists, but probably also for the potential mate. Paradoxically, that is why selection for intelligence, if it occurred, may be very strong. One has to be ... | [
{
"answer_id": 934,
"pm_score": 3,
"text": "<p>I know nothing about biology however I did watch an amazing PBS documentary on cuttlefish that I think is fairly relevent.</p>\n\n<p>From <a href=\"http://www.pbs.org/wgbh/nova/nature/kings-of-camouflage.html\">http://www.pbs.org/wgbh/nova/nature/kings-of-c... |
371 | <p>Can anyone summarize the mechanism by which when an object of a given temperature is placed in contact with, say, the skin on a human fingertip, the average speed of the particles of the object is converted into nerve signals to the brain?</p>
<p>If you can answer that, how about the format of how the temperature is encoded in the nerve signals?</p>
| [
{
"answer_id": 372,
"pm_score": 6,
"text": "<p>In the periphery (e.g. on our fingertips), our body senses external temperature through nerve terminals, expressing certain <a href=\"http://en.wikipedia.org/wiki/Transient_receptor_potential_channel\">TRP channels</a>. These are ion channels that are sensi... | [
{
"answer_id": 377,
"pm_score": 4,
"text": "<p>To complement on nico's answer (I don't have enough rep to comment), TRP channels seems to be also sensitive to increment or decrement of temperature as reported recently in a paper by Gallio <em>et al</em><sup><a href=\"http://www.sciencedirect.com/science... |
410 | <p>I was playing around with a simulation of the <a href="https://en.wikipedia.org/wiki/Hodgkin-Huxley_model" rel="noreferrer">Hodgkin-Huxley model</a> using their original parameters for the squid giant axon.</p>
<p>By applying a constant stimulation current to the model in resting state, an infinite train of action potentials is triggered, which seems reasonable. However, if the current exceeds a threshold, these APs die off very quickly as both the membrane potential and the ion conductances reach a steady state. </p>
<p>What is this phenomenon called? Is it a real phenomenon, or just an artefact of the Hodgkin-Huxley model?</p>
<p><a href="https://i.stack.imgur.com/kR5Hh.png" rel="noreferrer"><img src="https://i.stack.imgur.com/kR5Hh.png" alt="enter image description here"></a></p>
| [
{
"answer_id": 464,
"pm_score": 4,
"text": "<p>This phenomenon is called <em>depolarization block</em> and it occurs in real membranes in current-clamp experiments.</p>\n\n<p>The key mechanism is that the membrane has not been allowed to repolarize sufficiently to relieve the inactivation of sodium chan... | [
{
"answer_id": 414,
"pm_score": 2,
"text": "<p><em>(I probably ought to have a pat answer to this on the tip of my mind, but since I don't I'm going to wing it. This is probably just an opportunity to make an utter fool of myself. Please treat everything that follows with extreme suspicion.)</em></p>\n\... |
417 | <p>I understand that in normal REM sleep the voluntary muscles are in effect paralysed in order to prevent an individual acting out their dreams. <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2579974/">This paper</a> indicates that there are likley to be multiple causes of this atonia. I am interested to know <em>what are some of these methods by which natural atonia is achieved by the body in periods of sleep</em>?</p>
<p>Furthermore, <em>what causes these mechanisms to fail in individuals who suffer from sleep-walking</em>?</p>
| [
{
"answer_id": 1050,
"pm_score": 4,
"text": "<p>There's an excellent, comprehensive review article on the entire process of REM sleep:</p>\n\n<blockquote>\n <p>Vetrivelan,R, Chang, C, Lu,J (2011). Muscle tone regulation during REM sleep:\n neural circuitry and clinical significance. Archives Italienne... | [
{
"answer_id": 17040,
"pm_score": 0,
"text": "<p>Failure of maintaining atonia does not lead to sleep-walking but to REM sleep behavior disorder. Sleep-walking is a mixture of NREM and wakefulness.</p>\n\n<p>Mahowald, M. W., & Schenck, C. H. (2005). Insights from studying human sleep disorders. Natu... |
447 | <p>I can understand natural variation in alcohol dehydrogenase (ADH) in a population leading to variation in rate of inebriation (after controlling for other variables -- e.g., mass, food consumption, etc.).</p>
<p>But what physiological (adaptive?) process leads to increased alcohol tolerance over the long term in a single individual?</p>
| [
{
"answer_id": 633,
"pm_score": 5,
"text": "<p>The subject of alcohol tolerance is broader than it might appear. However, in most cases people refer to what is called metabolic alcohol tolerance. Based on your response to the comment made by Alexander Galkin, I assume that you also refer to metabolic al... | [
{
"answer_id": 637,
"pm_score": 3,
"text": "<p>So, judging by your answer to my comment you are most likely talking about so-called <strong>consumption-induced alcohol tolerance</strong>, that one might develop by regular drinking of alcoholic beverages.</p>\n\n<p>We can group the reasons for increased ... |
481 | <p>From all accounts, it seems as if the <em>Escherichia</em>, <em>Enterobacter</em>, etc. that live and thrive in the human gut are pretty well entrenched. I know that these microbial populations are often analyzed as an ecosystem.</p>
<p>What surprises me is that it seems like minor food poisoning can throw the whole ecosystem off. I know superficially that <em>Clostridium</em> are contenders in the fight because they remain viable after traveling through the acid of the stomach, but why are these populations so sensitive to other invading bacteria? </p>
| [
{
"answer_id": 484,
"pm_score": 5,
"text": "<p>There are two types of food poisoning:</p>\n\n<p><strong>Alimentary intoxication</strong></p>\n\n<p>This is the case when you consume food which is contaminated with some toxins, and those are responsible for development of the poisoning symptoms. The sourc... | [
{
"answer_id": 589,
"pm_score": 3,
"text": "<p>As requested, elaborating this into a full answer.</p>\n\n<p>Three things to consider:</p>\n\n<ol>\n<li>\"Alterations to gut microflora\" need not only be the invasion of a different, aggressive species of bacteria. One of the most common, and most dramatic... |
487 | <p>When I studied biology at my medical school, we used to learn topics around a century old: the famous Darwin's voyage on "Beagle" to the Galapagos Islands, the classical triad of his Theory of Evolution, etc.</p>
<p>At the same time we were told that there is no evidence found in nature for many of these statements of his evolutional theory. For example, people studied <a href="http://www.wildsingapore.com/news/20060304/060420-5.htm" rel="nofollow noreferrer">wildlife</a> around Chernobyl and found that no new species emerged due to much higher mutation rate as a consequence of radiation. On the contrary, there were <a href="http://www.monstersandcritics.com/science/nature/features/article_1158689.php/Chernobyl_radiation_no_problem_-_almost_-_for_Mother_Nature" rel="nofollow noreferrer">no significant differences</a> between the species living under elevated radiation level and those living in "normal" conditions.</p>
<p>Do these facts somehow influence our understanding of the theory of evolution? Are there any breakthrough findings which happened in the last 20 years that prove or disprove it?</p>
| [
{
"answer_id": 538,
"pm_score": 5,
"text": "<p>My friend Brightblades is right in one thing. It seems your teacher was working off a caricature of what the theory of evolution actually says. <a href=\"https://skeptics.stackexchange.com/questions/2057/demonstrable-and-repeatable-examples-of-evolution\"... | [
{
"answer_id": 68885,
"pm_score": 1,
"text": "<p>Perhaps the biggest advance since you studied evolution has been the sequencing of DNA and it's exhaustive analysis and decoding by computers and mathematicians.</p>\n\n<p>Previously the proofs of evolution were geographical, anatomical, genetic, fossil, ... |
514 | <p>I'm not a professional in biology nor a student, but I'm curious about this. To be more specific: why doesn't a plant virus affect animal cells?</p>
<p>I suspect that different kinds of cells have different ways to replicate DNA and that this is the reason for the specialization of viruses.</p>
<p>I wonder if someone in the field can explain this to me. Thanks.</p>
| [
{
"answer_id": 515,
"pm_score": 5,
"text": "<p>Firstly, it's important to recognize that \"plant viruses\" do not exist. There are only \"viruses that affect particular plant cells\", or \"viruses that affect a particular cell type\". You'll see why in a moment. </p>\n\n<p>One of the structural componen... | [
{
"answer_id": 536,
"pm_score": 3,
"text": "<p>Further to LanceLafontaine's answer I'd just like to mention that, although as he mentioned viruses interact with DNA replication in different ways, DNA replication in itself is the same process in both plant and animal cells. For example, a human cheek ce... |
517 | <p>This is at least partly an historical question, and I am not even remotely a biologist of any sort, so apologies beforehand if it's a little obscure.</p>
<p>I often wonder how many distinctions were made in pre-Renaissance times, between species of animals.</p>
<p>For example, though I'm sure there have always been those with enough of an interest in nature to tell subtle differences, how were lemmings or voles, for example, told apart from rats or mice? Or did this recognition of speciation only come later, once more detailed (intrusive) forms of analysis became common?</p>
<p>I've looked up the etymologies for vole, lemming and hamster and all are dated post-Renaissance, so at least in these instances it <em>may</em> be safe to assume that people might simply not have noticed the differences before closer study took place. But I guess there are other animals where the same question applies (particularly smaller, harder-to-scrutinise animals where there are a large number of species similar at a glance).</p>
<p>EDIT: <em>Vole</em> means field (same root as <em>wold</em>), giving rise to the 19th c. term <em>volemouse</em>, meaning that originally, mouse and vole were indeed seen as one and the same -- proof of point.</p>
<p>P.S. Of course, this question need not apply solely to animal species.</p>
| [
{
"answer_id": 518,
"pm_score": 4,
"text": "<p>The branch of science you are looking for is <em>taxonomy</em>, that is the science of identifying and naming species, and arranging them into a classification.</p>\n\n<p>Modern taxonomy was born from the studies of the Swedish zoologist Carl Linnæus (1707-... | [
{
"answer_id": 1331,
"pm_score": 3,
"text": "<p>If I understand <a href=\"http://www.goodreads.com/book/show/6518072-species\">John S. Wilkins' magnificent book on the history of the \"species\" concept</a> correctly, the basis of biological taxonomy can be traced back to the Aristotelian idea of <a hre... |
522 | <p>Clearly, a zygote does not harbor any microbes. As it develops, and the alimentary canal tissue is differentiated, I logically assume that there is still no microbial activity in the fetus's gut. I'm thus also assuming that the commencement of microbial activity in the intestines occurs after birth, but when, and how? </p>
<p>Do newborn babies just happen to ingest only certain e.g., <em>E.coli</em> strains? Is the gut a selective environment in which only certain <em>E.coli</em> strains develop? </p>
<p>Are there any mechanisms to ensure that harmful bacteria do not initially reside in the gut? Is a newborn's digestive tract particularly unstable and ineffective until the proper microbes are established?</p>
| [
{
"answer_id": 525,
"pm_score": 5,
"text": "<blockquote>\n <p>The gastrointestinal tract of a normal fetus is sterile. During birth and rapidly thereafter, bacteria from the mother and the surrounding environment colonize the infant's gut. Immediately after vaginal delivery, babies may have bacterial s... | [
{
"answer_id": 523,
"pm_score": 4,
"text": "<p>The initiation of gut flora come from maternal cervical and vaginal flora (Bezirtzoglou, 1997)<sup><a href=\"http://www.ncbi.nlm.nih.gov/pubmed/16887585\">1</a></sup>. These predominantly include facultative anaerobes (e.g., <em>Staphylococcus</em>, Enterob... |
550 | <p>If all the brain ever "sees" is action potentials, how do we know that one set of action potentials denotes a flash of light, another one signifies a loud sound, etc ?</p>
| [
{
"answer_id": 558,
"pm_score": 5,
"text": "<p>The fundamental way in which this works is by geography: signals triggered by different stimuli travel by different pathways to different regions of the brain that are specialised for dealing with the sorts of information they contain.</p>\n\n<p>For example... | [
{
"answer_id": 572,
"pm_score": 3,
"text": "<p>Just adding some metaphors in support to the excellent answer by <a href=\"https://biology.stackexchange.com/users/149/walkytalky\">walkytalky</a>.</p>\n\n<p>Our brain is like a huge processing center that can be seen from techni's prospective as a sort of ... |
554 | <p>I have some question, which I'm sure would fit better in the fitness section but proper answers should probably come from someone that knows biology.</p>
<p>My question is rather simple. How can a person that doesn't eat any vegetables at all be affected by such a diet? By no vegetables at all, I mean not eating any ever.</p>
| [
{
"answer_id": 566,
"pm_score": 5,
"text": "<p>There is a list of several implications of not eating vegetables (references <a href=\"http://www.livestrong.com/article/468537-what-will-happen-if-you-dont-eat-vegetables/\">1</a>, <a href=\"http://commonsensehealth.com/Diet-and-Nutrition/Vegetables_List_w... | [
{
"answer_id": 15654,
"pm_score": 0,
"text": "<p>You'd be deprived of the vitamins and minerals which are found only in vegetables, but you'd live. There are vitamins and minerals in meat and other foods, plenty of them, and your metabolism would adapt to produce the proteins which are missing. Human bo... |
574 | <p>If the <em>aim</em> of evolution is to allow an organism to better compete against rivals, why would stabilizing selection ever happen? If you're not selecting the most highly adapted competitors at either end of the spectrum then how would a species progress? </p>
| [
{
"answer_id": 575,
"pm_score": 6,
"text": "<p>It occurs when a beneficial characteristic has been developed over time and it would be harmful to stray from it. In these cases it is not the individuals at the fringe (as you put it the <em>most adapted</em>) who are the best adapted. </p>\n\n<p>I think ... | [
{
"answer_id": 590,
"pm_score": 3,
"text": "<p><strong>Evolution has no aim</strong>, you seem to be repeating a caricature of what the theory of evolution really says. Evolution works by a mechanism where pressures on a population select for the traits that are best suited for that environment. If th... |
619 | <p>What is the ideal amount of RNA to use for the RT? and how much cDNA to use then for the PCR?</p>
<p>I did RT with a solution of RNA of 0.36 ug/ul. Then for my PCR I used 1 ul of the cDNA obtained and used 25 cycles because I was hoping to see a difference between an endogenous level and an overexpression. However, I detected no band at the expected height of 500 bp but a diffuse band at 100 bp. What can this 100 bp represent? primer dimer? I switched to 35 cycles and I used either the same amount of cDNA or add 3 times more cDNA. In both cases I got bands at the expected height (but stronger when I put more cDNA) and still big bands at 100 bp. </p>
| [
{
"answer_id": 636,
"pm_score": 4,
"text": "<p>I see big fuzzy bands around 100bp as well. They're most likely <strong>RNA contamination</strong>. To get rid of them, digest your RT-PCR products with RNAse-H. But if you just need to visualize your band of interest, and the fuzzy bands aren't getting in ... | [
{
"answer_id": 629,
"pm_score": 2,
"text": "<p>There is no single \"ideal amount\" of RNA. I would suggest you to do a titration curve to determine the best amount for your specific assay. The band at 100 bp could be a non-specific amplification. You could try to increase slightly the annealing temp to ... |
642 | <p>Hope this is within the scope of this site.</p>
<p>Color-deficient persons lack the cells in their retina needed for differentiating some (or all) colors.</p>
<p>However, the part of the brain that actually processes images is not deficient.</p>
<p>Is it possible to somehow make a color-deficient person "see" the missing colors by directly activating that part of the brain responsible for processing colors?</p>
| [
{
"answer_id": 652,
"pm_score": 4,
"text": "<p>It is a very interesting question and I did some efforts to investigate the literature on this topic, but yet <strong>I don't have a definitive answer for you</strong>. But let's start from the beginning.</p>\n\n<p>First of all, the reason for color deficie... | [
{
"answer_id": 3454,
"pm_score": 2,
"text": "<p>Yes! And no. But first, some background.</p>\n\n<p>Your central nervous system has (or is believed to have, as do other primates) a number of different organizational structures. Cells within a column (the cortex is composed of about 7 layers, and a col... |
651 | <p>Is there any hypothesis on the minimum number of amino acids required for life?</p>
| [
{
"answer_id": 666,
"pm_score": 5,
"text": "<p>You can divide the 22 (including <a href=\"https://en.wikipedia.org/wiki/Selenocysteine\">selenocysteine</a> and <a href=\"https://en.wikipedia.org/wiki/Pyrrolysine\">pyrrolysine</a>) proteinogenic amino acids into broad groups of similar amino acids. Ther... | [
{
"answer_id": 82312,
"pm_score": 0,
"text": "<p>If you allow for the <a href=\"https://en.wikipedia.org/wiki/RNA_world#Implications_of_the_RNA_world\" rel=\"nofollow noreferrer\">\"RNA world\"</a> hypothesis, then the minimum number of amino acids needed for life would be zero, because RNA in that cont... |
656 | <p>What is the largest perennial herbaceous plant? My guess would be some kind of banana or bamboo.</p>
| [
{
"answer_id": 54713,
"pm_score": 3,
"text": "<p>The tallest banana species is Musa Ingens (15m) which grows in the forest of Papua New Guinea and Indonesia. It also claimed as the the world's largest herbaceous plant. <a href=\"http://www.thestatworld.com/2015/12/musa-ingens-the-tallest-banana-plant-in... | [
{
"answer_id": 724,
"pm_score": 3,
"text": "<p>As mentioned above, the largest perennial herbaceous plant is indeed the banana. Whilst the main reference to this (\"Yes, we have more bananas\" - an article in the Royal Horticultural Society Journal from May 2002) has been removed from their website it ... |
681 | <p>Much discussion has been had about the affects of climate change on plantlife, but how will rising carbon dioxide concentrations affect the photosynthetic process itself? Since CO₂ is a reagent in photosynthesis, would we expect higher CO₂ to mean an increased rate of photosynthesis in a real-world context? Has there been any research on this? </p>
<p>I am thinking more of large-scale field tests rather than lab plants.</p>
| [
{
"answer_id": 863,
"pm_score": 5,
"text": "<p>There are several key ways in which rising atmospheric CO₂ concentrations will affect photosynthesis, and these are related to the different types of photosynthesis. In order to properly answer your question, I'll provide some background about photosynthesi... | [
{
"answer_id": 1722,
"pm_score": 4,
"text": "<p>I wanted to add a little more to the excellent answer above, especially since the OP asks about research into this question in a \"real-world context\". </p>\n\n<p>There is a substantial body of evidence on exactly this question that comes from experiments... |
684 | <p>In my research, I look at a lot of gene predictions / annotations. Frequently, I see loci where multiple gene models overlap. I haven't taken a systematic approach to analyzing these cases, but I do remember seeing quite a bit of variation in the direction of the overlapping genes (same vs different directions), the amount of overlap, and even the number of overlapping genes.</p>
<p>I know enough about gene prediction to take any computational predictions with a grain of salt--even those supported by transcript and peptide alignments. However, these cases have me thinking--does overlap of genetic information <em>really</em> occur in eukaryotes? I seem to remember learning (or hearing anecdotally) that it can happen in prokaryotes, and that seems to be understandable given the compactness of prokaryotic genomes. But can this happen in eukaryotes? Has this been studied, and are there cases that have been confirmed experimentally?</p>
| [
{
"answer_id": 685,
"pm_score": 4,
"text": "<p>You might be interested in the INK4A locus (chromosome 9p), encoding both p19 and p16 genes, very close to p15. You can read a description <a href=\"http://www.ncbi.nlm.nih.gov/books/NBK13507/\"><strong>here</strong></a>. All three proteins are known experi... | [
{
"answer_id": 723,
"pm_score": 2,
"text": "<p>In general, the compactnes of genomes is a characteristic of prokaryotes, but there are several eykaryotes that have overlapping genes: many parasites and endosymbionts. The best studied of these are the fungal parasites of the phylum <a href=\"http://en.wi... |
686 | <p>I know that most nitrogen is fixed through industrial processes and bacterial symbiotic relationships. However, are there any plants that can fix their own atmospheric nitrogen?</p>
| [
{
"answer_id": 896,
"pm_score": 4,
"text": "<p>There are no known plants that fix their own nitrogen. <strong>However, there soon may be!</strong></p>\n\n<p>Because N is the major limiting factor in agricultural productivity, there is huge interest in plant systems which can fix their own. It's importan... | [
{
"answer_id": 696,
"pm_score": 3,
"text": "<p>As far as I know, all biotic nitrogen fixation is performed by prokaryotic organisms such as <em>Rhizobium.</em> I don't know of any plants which can carry out this function on their own.</p>\n\n<p>Plants can't use atmospheric N<sub>2</sub> because it is he... |
700 | <p>I know someone who bought earphones that shine light in you ears. According to what he was told, there are neurons that sense light and then make you feel wide awake when activated, which seemed like snake oil to me. Apparently the pineal gland may be able to sense light and it does secrete melatonin - a sleep regulating hormone. I'm still sceptical though as its stuck in the middle of your brain. Would shining lights in your ears be able to have any effect on how awake you feel?</p>
| [
{
"answer_id": 705,
"pm_score": 5,
"text": "<p>There is no known mechanism for light detection through the ears in humans, as far as I know. It is certainly true that the pineal gland is part of the system that regulates the circadian rhythm (briefly, the daily sleep-wake cycle). However, while the pine... | [
{
"answer_id": 704,
"pm_score": 2,
"text": "<p>I believe there are light sensors (<a href=\"http://en.wikipedia.org/wiki/TRPV3\" rel=\"nofollow\">TRPV3</a>) in the skin for infrared light (heat), that convey that information back to the brain from the skin. This is kind of light detection, but it is no... |
729 | <p>Following up on <a href="https://biology.stackexchange.com/questions/306/how-many-human-proteins-have-a-solved-3d-structure">How many human proteins have a solved 3D structure?</a>,is there a list of very well characterized human proteins / protein complexes? </p>
<p>My criteria for "very well characterized" includes, at least:</p>
<ul>
<li>a high quality 3D structure</li>
<li>known activity <em>in vivo</em></li>
<li>known associates in its activities in the cell</li>
<li>kinetics of its activity</li>
<li>regulatory elements for expression</li>
<li>etc..., and</li>
<li>(probably most importantly) a general consensus among experts that it is well described</li>
</ul>
<p>This list would most likely include such proteins or protein complexes as: </p>
<ul>
<li>P53, </li>
<li>polymerase alpha, and </li>
<li>the nuclear pore complex,</li>
</ul>
<p>to name a very small number.</p>
| [
{
"answer_id": 736,
"pm_score": 4,
"text": "<p>To address your list:</p>\n\n<ul>\n<li>a high quality 3D structure: this you can easily get from PDB, using the answers to the question you linked as starting point. However, it is become increasingly clear that <a href=\"http://en.wikipedia.org/wiki/Intrin... | [
{
"answer_id": 3578,
"pm_score": 1,
"text": "<p>Many of these questions can be answered by UniProt:</p>\n\n<ul>\n<li><p>around 4,600 proteins with some 3D structure (<a href=\"http://www.uniprot.org/uniprot/?query=%28organism:9606%29%20AND%20reviewed%3ayes%20AND%20keyword%3aKW-0002&sort=score\" rel=... |
753 | <p>Many flying insects tend to have very jagged trajectories. For moves of a fruit fly looks like a <a href="http://en.wikipedia.org/wiki/Random_walk">random walk</a>.</p>
<p>Is there any research on the properties of trajectories (e.g. their fractal dimension or mathematical models producing similar behaviour)?</p>
<p>Besides the path of a single insect, I am also interested in the interaction of a small number of insects (e.g. 2 or 3).</p>
<p>I am aware of the research in flocking and swarming (e.g. Tamas Vicsek, Anna Zafiris, <a href="http://arxiv.org/abs/1010.5017">Collective motion</a> 2010) and of techniques of obtaining such trajectories (e.g. Danping Zou, Yan Qiu Chen, <a href="http://dx.doi.org/10.1109/ICCVW.2009.5457649">Acquiring 3D motion trajectories of large numbers of swarming animals</a> or an <a href="http://users.soe.ucsc.edu/~manazhao/files/iccv09_voec.pdf">open access pdf</a>, 2009). However, I haven't found within them an answer to my particular question.</p>
| [
{
"answer_id": 807,
"pm_score": 4,
"text": "<p>Quick search - Some articles that may interest you:</p>\n<ol>\n<li><p>Random walk model of insect movements\n<br>\n<a href=\"https://doi.org/10.1007%2FBF00379695?from=SL\" rel=\"nofollow noreferrer\">Kareiva P. M., Shigesada N. (1983). Analyzing insect move... | [
{
"answer_id": 758,
"pm_score": 5,
"text": "<p><a href=\"http://icb.oxfordjournals.org/content/45/2/274.full\" rel=\"nofollow noreferrer\">Dickinson (2005)</a> has a good review of insect flight, including behavior, biomechanics, electrophysiology, and neural control with links to more of the primary li... |
755 | <p>In animals temporary anaerobic respiration leads to the breakdown of the pyruvate formed by glycolysis into lactate. The buildup of lactate in the bloodstream is accompanied by a large number of protons causing lactic acidosis, which is detrimental to the health of the organism. This is one of the main suggestions I have come across for why a lack of oxygen is fatal to cells, however the LD<sub>50</sub> for lactic acid as referenced by the <a href="http://www.sciencelab.com/msds.php?msdsId=9924446">COSHH MSDS</a> seem awfully high (even if the route is by ingestion rather than directly into the bloodstream) for this to be a cause of cell death:</p>
<blockquote>
<p><strong>Toxicological Data on Ingredients:
ORAL (LD50): Acute:</strong> </p>
<p>3543 mg/kg [Rat (Lactic Acid (CAS no. 50-21-5))]. </p>
<p>4875 mg/kg [Mouse (Lactic Acid (CAS no. 50-21-5))].</p>
</blockquote>
<p>I also wonder if this is a larger problem for an organism as a whole rather than on a cellular level.</p>
<p>The alternative, I suppose, is that glycolysis alone does not provide sufficient ATP for vital cellular processes to occur. If this is the case, which ATP requiring processes are most vital for the short term survival for a cell? </p>
| [
{
"answer_id": 760,
"pm_score": 5,
"text": "<p>Here's an illustrated example in neurons:</p>\n\n<p>ATP, of course, is generated by aerobic respiration. The critical biochemical reaction in the brain that is halted due to lack of ATP (and therefore O2) is the glutmaine synthetase reaction, which is very ... | [
{
"answer_id": 774,
"pm_score": 2,
"text": "<p>Energy production starts with glycolysis, which generates NADH and pyruvate. Pyruvate goes to the mitochondria to make more NADH (or FADH2, which is similar to NADH) in the Krebs Cycle. NADH is used to power the electron transport chain, which gives most ... |
761 | <p>I am curious how Gall Wasps, bacteria and other organisms induce <a href="http://en.wikipedia.org/wiki/Gall">galls</a> to form. </p>
<p>Specifically, what chemicals induce gall formation?</p>
| [
{
"answer_id": 860,
"pm_score": 5,
"text": "<p>I'd like to add to Amy's excellent answer.</p>\n\n<p>Generally, galls are induced by the forced accumulation of plant hormones at different levels to those naturally maintained by the plant, in a localised area. Usually the hormones targeted are auxins and ... | [
{
"answer_id": 792,
"pm_score": 4,
"text": "<p>It seems not much is known about how insects induce gall formation (perhaps someone with more of an entomology can jump in). </p>\n\n<p>But we do know quite a bit about <em>Agrobacterium tumefaciens</em>, which causes crown gall in roses, grapes, and other ... |
781 | <p>Is it possible to trace the descent of a person only using his/her genome sequence?</p>
| [
{
"answer_id": 784,
"pm_score": 4,
"text": "<p>In short, yes, it is possible. There are companies that sequence part of your genome and then can trace it back to your ancestors. All human family trees can be traced back to their African origin 200 000 years ago, but the companies that sequence your gene... | [
{
"answer_id": 1061,
"pm_score": 2,
"text": "<p>Back when I was doing my PhD, there was a group in the same department as me working on an interesting project exploring the extent to which surnames (generally paternally inherited, at least in the modern west) and Y chromosomes (always paternally inherit... |
789 | <p>I wonder whether there is any intelligent decision-making in mitochondria in the timing of their operation.</p>
<p>Do they simply begin ATP production as soon as the correct reactants are present?</p>
<p>Or, because they have their own DNA, do they have more complex strategies that vary to benefit the mutual cooperation with the host cell? This assumes that the simple circular DNA is performing higher level decisions in switching.</p>
| [
{
"answer_id": 791,
"pm_score": 5,
"text": "<p>Mitochondria are comprised of ~3000 proteins. However, the mitochondrial genome has only 13-14 protein-encoding genes. The remaining 99.6% of mitochondrial proteins are encoded by genes in the nuclear genome. (<a href=\"http://en.wikipedia.org/wiki/Human_mi... | [
{
"answer_id": 790,
"pm_score": 3,
"text": "<p>The <a href=\"http://www.wiley.com/legacy/college/boyer/0470003790/structure/pfk/pfk_intro.htm\">textbook</a> version for the regulation of ATP involves a feedback loop with phosphofructokinase (PFK). The relative concentrations of ADP and ATP are character... |
793 | <p>I have a question I would like to pose to the community. I have recently received access to a bench-top ion torrent DNA sequencer. Our idea is to use this machine to sequence the DNA from patient’s tumors in order to guide treatment options. My job is to identify a list of all currently used anti-neoplastic drugs along with their known targets (i.e., specific genes and mutations) and accession numbers. I would like to put these data in a table in which each row corresponds to a different drug.</p>
<p>For example, a row in the table might read (column names are indicated in brackets): [disease] breast cancer, [drug] trastuzumab, [drug target] HER2/neu receptor, [gene] ERBB2, [location] chr17:37844393-37884915, [mutation type] amplification, [accession number] ENSG00000141736. The pathologists would then be able to use this database in order to select appropriate genes for sequencing whenever they receive a tumor specimen. If the patient’s tumor had an amplified ERBB2 gene, they could be given trastuzumab.</p>
<p>Currently our study is in pre-planning stages (i.e., we won’t actually be testing this on patients any time soon). I would appreciate it if anyone could give me on advice on how to go about creating such a database. I am aware of online databases including COSMIC, Sanger's Cancer Gene Census, and the Potential Drug Target Database (PDTD), but they don’t have everything that I’m looking for. I am familiar with R and could use it to combine data from multiple sources if necessary. If anyone else has comments or suggestions for further reading that would also be appreciated. Thanks!</p>
<p>Note: This question has also been posed on a Research Gate forum: <a href="http://www.researchgate.net/topic/Cancer_Biology/post/Looking_for_a_cancer_drug_target_database_to_guide_sequencing_of_patient_tumor_DNA">http://www.researchgate.net/topic/Cancer_Biology/post/Looking_for_a_cancer_drug_target_database_to_guide_sequencing_of_patient_tumor_DNA</a></p>
| [
{
"answer_id": 791,
"pm_score": 5,
"text": "<p>Mitochondria are comprised of ~3000 proteins. However, the mitochondrial genome has only 13-14 protein-encoding genes. The remaining 99.6% of mitochondrial proteins are encoded by genes in the nuclear genome. (<a href=\"http://en.wikipedia.org/wiki/Human_mi... | [
{
"answer_id": 790,
"pm_score": 3,
"text": "<p>The <a href=\"http://www.wiley.com/legacy/college/boyer/0470003790/structure/pfk/pfk_intro.htm\">textbook</a> version for the regulation of ATP involves a feedback loop with phosphofructokinase (PFK). The relative concentrations of ADP and ATP are character... |
809 | <p>I have heard and read about Peter's rule informally in the past, but never saw a formal definition or description. </p>
<p>Informally I have learned to understand Peter's rule as the assumed correlation between the amount of overlap between axons and dendrites and the post synaptic density in the synapse. Here is <a href="https://www.google.com/#sclient=psy-ab&q=%22peter%27s+rule%22+neuroscience">a sample</a> of the search results in Google.</p>
<p>Is my interpretation correct? Is there a more rigorous, perhaps quantitative, definition of Peter's rule? </p>
| [
{
"answer_id": 819,
"pm_score": 4,
"text": "<p>I think that your interpretation is correct, although <em>Principles of Neural Science</em> (Kandel et al.) doesn't mention Peter's rule (which is where I would have hoped to find a simple explanation).</p>\n\n<p>According to <a href=\"http://www.neuro.cjb.... | [
{
"answer_id": 8035,
"pm_score": 1,
"text": "<p>Here is a definition taken from <a href=\"http://www.scholarpedia.org/article/Computational_neuroanatomy#Potential_synaptic_connectivity_between_individual_cells\" rel=\"nofollow\">a Scholarpedia article on computational neuroanatomy</a>:</p>\n\n<blockquot... |
824 | <p>What I mean by "randomized" is, in the place where an egg cell or sperm cell is made, what is the mechanism by which each one is not made identically? Though I am a layman, I'm pretty sure that if the sperm cell that was right next to "me" had made it to the egg instead of the one that did, the resultant human would have a different genomic sequence and different features.</p>
| [
{
"answer_id": 827,
"pm_score": 4,
"text": "<p><a href=\"http://en.wikipedia.org/wiki/Meiosis\" rel=\"nofollow noreferrer\">Meiosis</a> is the type of cell division responsible for the diversification of genetic material among egg and sperm cells. The diversity comes primarily from <a href=\"http://en.w... | [
{
"answer_id": 828,
"pm_score": 1,
"text": "<p>I think we can attribute this to sheer probability. The human genome contains around 3 billion base pairs. When you consider recombination from chromosomal crossover that occurs in germ line cells, there is an astronomically huge number of possible unique c... |
837 | <p>I often hear that people who are taking antibiotics experience wild fluctuations between feeling full of energy and completely alert but soon after feeling impossibly fatigued and sick.</p>
<p>Does this have anything to do with the antibiotics being used by the body as anything? For example as a hormone or as a source of nutrition? Is this this a reported side effect when used for other infections?</p>
| [
{
"answer_id": 930,
"pm_score": 4,
"text": "<p>I have never heard about this phenomenon from my patients or professors at the Medical School, but this is a possible mechanism that comes to my mind.</p>\n\n<p>One of the classification for antibiotics takes consideration the effect on bacteria. Two possib... | [
{
"answer_id": 21397,
"pm_score": 2,
"text": "<p>\"There are antibiotics which contain carbohydrates, such as Gentamycin and Streptomycin (the aminoglycosides). These must be the antibiotics that could account for this phenomenon.\"</p>\n\n<p>My conjecture that the carbohydrate moities contained within ... |
849 | <p>I picture a neuron as having multiple trees of dendrites attached to the cell body with a single axon leaving the cell body. I believe the cell body near the axon root makes the decision to fire or not fire an action potential.</p>
<ul>
<li><p>If the neuron has both excitatory and inhibitory synapses in the dendrite trees, how do these communicate to the cell body? </p></li>
<li><p>Does something like an action potential get transmitted down the dendritic trees to the cell body? </p></li>
<li><p>What is the difference between the excitatory and inhibitory signals that are transmitted?</p></li>
</ul>
| [
{
"answer_id": 852,
"pm_score": 4,
"text": "<p>From your comment to nico's good answer, it seems that your question is really about how synaptic potentials propagate through dendrites.</p>\n\n<p>Canonically, synaptic potentials travel passively along membranes and is described by <a href=\"http://en.wik... | [
{
"answer_id": 850,
"pm_score": 4,
"text": "<p>An inhibitory synapse works just like an excitatory one!</p>\n\n<p>When a presynaptic neuron fires it will release a neurotransmitter at its terminal(s). This neurotransmitter can be excitatory or inhibitory, the main excitatory one in the central nervous s... |
875 | <p>An exam question asked what stage of meiosis corresponds with "first meiotic arrest of oogenesis". I can't work out the answer from <a href="http://en.wikipedia.org/wiki/Meiosis" rel="nofollow">the wiki page</a> - can anyone explain which step this refers to?</p>
| [
{
"answer_id": 15601,
"pm_score": 4,
"text": "<p>When females are in their mother's womb all their Oogonium (plural Oogonia) are being made, they they undergo mitotic divisions to become a primary oocyte. Then, the primary oocytes start to undergo meiosis I - but meiosis I is arrested. This is the firs... | [
{
"answer_id": 901,
"pm_score": 3,
"text": "<p>Meiosis consists of two divisions. Both are somehow similar to \"ordinary\" type of cell division - mitosis, but there is no DNA replication between them. As mitosis, each of two meiosis divisions might be divided into 5 stages: </p>\n\n<ol>\n<li>Profaze (c... |
889 | <p>Can anyone suggest a dye which specifically targets DNA, but is not fluorescent? We plan to mark DNA before observing it with RAMAN-Spectroscopy. Because of the weak signal, even a low emission would disturb the reading.</p>
| [
{
"answer_id": 890,
"pm_score": 3,
"text": "<p>One option is to use <a href=\"http://en.wikipedia.org/wiki/Biotinylation\" rel=\"nofollow\">biotin labelling</a>. Most molecular biology supply companies do kits for this, and supply biotinylated nucleotides.</p>\n"
}
] | [
{
"answer_id": 1067,
"pm_score": 0,
"text": "<p>Methylene blue? Certainly not as sensitive or specific as other options but it's cheap and does not fluoresce.</p>\n"
}
] |
904 | <p>I recently extracted RNA from developing plant leaves for the first time, as part of a very long and intensive experiment. The samples were extremely precious because of the amount of effort that went into obtaining them (harvesting thousands of miniscule leaves, one from each plant, to get the required mass).</p>
<p>I extracted the RNA with TRIzol and chloroform. Nanodrop showed excellent yield as you would expect for actively growing young tissue, but some of the samples had really low 260/230 ratios. I know this suggests phenol or salt contamination, but what can I do to clean the samples without losing any of the precious RNA? And how can I avoid the contamination in the future?</p>
| [
{
"answer_id": 907,
"pm_score": 4,
"text": "<p>You can clean up phenol by washing with choloroform, and then doing an isopropanol precipitation followed by a 75% EtOH wash (let me know if you'd like an exact protocol).</p>\n\n<p>To avoid contamination (and sample loss), you have to be meticulous in your... | [
{
"answer_id": 950,
"pm_score": 3,
"text": "<p>An ethanol precipitation should work. But I have had great success using the Qiagen RNA cleanup columns, which are in my opinion easier. Here is a URL to see the RNA cleanup columns Qiagen offers: <a href=\"http://www.qiagen.com/products/rnacleanupconcent... |
910 | <p>Will it travel more slowly since it hasn't had food for a day?</p>
<p>What if I left the cup there for longer?</p>
| [
{
"answer_id": 918,
"pm_score": 4,
"text": "<p>Just solely in terms of not having food (ignoring the importance of O<sub>2</sub> that Ramkryp has pointed out), spiders don't necessarily have to feed on a daily basis anyway. It's not the same species of spider as you ask about in your question, but cons... | [
{
"answer_id": 947,
"pm_score": 5,
"text": "<p>To answer the first part of your question: it is extremely unlikely that the spider will die or be weakened after just one day.</p>\n<p>Wolf spiders (Lycosids) are all predators. Due to variations in prey populations, and low efficiency of consumption at hi... |
926 | <p>Is it possible for a virus to live symbiotically with its host?
Is the human body plagued with viral infections that do negligible harm, or even serve a beneficial role?</p>
| [
{
"answer_id": 981,
"pm_score": 6,
"text": "<p>It is possible for viruses to live in mutualistic relationships with their hosts, these associations are often overlooked due to the devastating effect that many viruses can have.</p>\n\n<p>To give an example in humans, when HIV-1-infected patients are also... | [
{
"answer_id": 980,
"pm_score": 3,
"text": "<p>As mentioned <a href=\"https://biology.stackexchange.com/questions/158/why-is-there-an-extended-delay-before-g-m-liver-cells-are-attacked-by-the-immun\">in this question</a> , Adeno-associated virus is often used for gene therapy. This is due largely to it... |
937 | <p>Evolution is often mistakenly depicted as linear in popular culture. One main feature of this depiction in <a href="http://www.youtube.com/watch?v=faRlFsYmkeY">popular</a> <a href="http://www.youtube.com/watch?v=R795KiMD4zs">culture</a>, but even <a href="http://www.youtube.com/watch?v=jHoxZF3ZgTo#t=2m51">in science popularisation</a>, is that some ocean-dwelling animal sheds its scales and fins and crawls onto land.</p>
<p>Of course, this showcases only <em>one</em> ancestral lineage for <em>one</em> specific species (<em>Homo sapiens</em>). My question is: <strong>Where else did life evolve out of water onto land?</strong></p>
<p>Intuitively, this seems like a huge leap to take (adapting to a fundamentally alien environment) but it still must have happend several times (separately at least for plants, insects and chordates, since their respective most recent common ancestor is sea-dwelling). In fact, the more I think of it the more examples I find.</p>
| [
{
"answer_id": 939,
"pm_score": 8,
"text": "<p>I doubt we know the precise number, or even anywhere near it. But there are several well-supported theorised colonisations which might interest you and help to build up a picture of just how common it was for life to transition to land. We can also use know... | [
{
"answer_id": 2560,
"pm_score": 6,
"text": "<p>Richard's answer is fantastic, and I'm not going to be as thorough. But here's some other examples:</p>\n\n<ul>\n<li>Turtles (which did sea to land to sea back to land!) </li>\n<li>Gastropoda (snails and slugs)</li>\n<li>Tardigrada (water bears)</li>\n<l... |
940 | <p>Each time I'm too lazy too cook I think it'd be cool to be able to just plug myselt into an outlet. Yet I know it is not possible - I need amino acids and a lot of other stuff that electricity can't replace.</p>
<p>Can some simple organism live on electricity alone or is it just fundamentally impossible?</p>
| [
{
"answer_id": 944,
"pm_score": 4,
"text": "<p>No; the problem is, as you pointed out, that no organism will manage to multiply, grow or even sustain itself without absorbing matter to create new cells and fill metabolic losses.</p>\n\n<p>Even photoautotrophic organisms which get energy from light (whic... | [
{
"answer_id": 1764,
"pm_score": 1,
"text": "<p>The cells would have to produce glucose directly from electricity. If we figured that out we could also solve our energy crisis.</p>\n"
}
] |
961 | <p>In protocols for polyacrylamide gel electrophoresis (PAGE) I often see instructions to degas the gel solution by putting it under vacuum for 10-15 minutes before polymerizing the gel. </p>
<p>I usually don't do this, and when I tried it once I couldn't see any difference. So I'm wondering what exactly the degassing is meant to achieve and how big the effect should be.</p>
<ul>
<li>What effect is degassing the gel solution supposed to have?</li>
<li>How important is degassing to achieve good gels?</li>
</ul>
<p>Any literature that examines the effect of degassing would be appreciated.</p>
| [
{
"answer_id": 962,
"pm_score": 5,
"text": "<p>The reason for degassing your gels is to remove oxygen. Oxygen in the gel interferes with polymerisation, slowing it down and making it less consistent, so degassing makes it faster and more uniform.</p>\n\n<p>From the <a href=\"http://www.encorbio.com/prot... | [
{
"answer_id": 1517,
"pm_score": 2,
"text": "<p>I have been running gels with different Acrylamide/Bisacrylamide ratios recently. People usually work with 1:37.5, 1:29 ratios which are commonly used for DNA and Protein gels. I have noticed that when you work with lower ratios 1:200 - 1:500, degassing be... |
968 | <p>The book said when you look at object close to you, the eye muscles contract and vice versa. I wonder what will be the status of the eye muscles when I stare at distance view (such as a mountain) inside an office through a glass wall. The mountain is far away but the glass wall is close to us. In this case, does the eye muscles relax?</p>
| [
{
"answer_id": 970,
"pm_score": 4,
"text": "<p>In the situation you describe, the eye would be focused on the distant mountain. This would mean that the lens would be stretched and thin in order to minimize the focussing power of the eye. <em>Therefore the ciliary muscles would be relaxed</em>. </p>... | [
{
"answer_id": 1068,
"pm_score": 2,
"text": "<p>To increase long range focus, the ciliary muscle is relaxed so that the zonular fibres flatten the lens. This flattening increases the focal distance and far away objects appear sharp.\nThe process is reversed when increasing short range focus.</p>\n\n<p>I... |
972 | <p>I work in a lab where all the pipettes are shared. We often have visiting students who come and use the pipettes for a short project. So when I work with them, they might have been handled by other people several times since I last used them. This leads me to worry that they might have been mishandled, or become less accurate somehow.</p>
<p>How do I clean and calibrate pipettes? And how often do I need to do it?</p>
| [
{
"answer_id": 976,
"pm_score": 4,
"text": "<p>How often you should calibrate your pipettes depends on the tolerances of your application. For some applications, like quantitative PCR setup, one may care a great deal; for general lab work, one can probably be less particular. You can get a sense of how ... | [
{
"answer_id": 977,
"pm_score": 2,
"text": "<p>When doing a recent investigation into methods of quantitatively determining the concentration of aspirin in solution I found <a href=\"http://www.pipette.com/support/onlinelecture/sop%20sample%20of%20pipette%20calibration%20procedure.pdf\" rel=\"nofollow\"... |
1,034 | <p>I've heard that stomach lining has the fastest reproducing cells and the brain has the slowest.</p>
<p>Where in the human body does mitosis occur and at what rates do these cell reproduce? Is there a chart for the whole body available?</p>
| [
{
"answer_id": 1036,
"pm_score": 4,
"text": "<p>In many cases cell division depends on the stage of development an organism is in. The rate of cell division is obviously much faster in a developing organism and from what I understand fully differentiated cells such as neuron and those in skeletal muscle... | [
{
"answer_id": 16278,
"pm_score": 2,
"text": "<p>Question is two years old, and the answer is approx 20 yo, but I believe both are still pertinent: According to Jared Diamond on pg 12 of his Harper paper version (1993 -- but reissued in 2006) of The Third Chimpanzee, we replace intestinal lining epithel... |
1,041 | <p>During photosynthesis, a plant translates CO<sub>2</sub>, water and light into O<sub>2</sub>. I assume the carbon C is further used for the growing process. I wonder how the plant grows <em>before</em> the time where photosynthesis is possible, i.e. before there are even leaves, in which photosynthesis occurs.</p>
<blockquote>
<p>To what extent does the plant grow from the seed/the minerals in the ground?</p>
<p>How much carbon are relevant for which parts of the plant and at what times of the evolution of the plant?</p>
</blockquote>
<p>I don't know if there are only these life periods of the plant, i.e. if there are other major biochemist-of-growing changes, than in the comparison before and after the plant got leaves. So are there other relevant aspects to this? If there <em>are</em> leaves present, is the rigid structure of the plant only coming from the CO<sub>2</sub> in the air and not from the ground anymore?</p>
<p>The answer will probably depend on the plant. So here is another formulation of the question:</p>
<blockquote>
<p>What are typical characteristics of different plants in this regard? I.e., how do common species of plants manage their C consumption before (and after) the development of leaves?</p>
</blockquote>
| [
{
"answer_id": 1042,
"pm_score": 6,
"text": "<p>There are quite a few questions and thoughts in there, I'll try to cover them all:</p>\n\n<p>First, to correct your initial word equation: <strong>During photosynthesis, a plant translates CO<sub>2</sub> and water into O<sub>2</sub> and carbon compounds us... | [
{
"answer_id": 45535,
"pm_score": 1,
"text": "<p>Simply put. Plant growing from sugar (both energy and material). So if they could store sugar (or even find sugar from anywhere). They could grow even there are no sunlight</p>\n\n<p>And photosynthesis never make plant grow immediately. It just make sugar... |
1,090 | <p>From what I understand, bacteria have circular DNA. What advantages does it have over linear strands like for eukaryotes? </p>
<p>Do there exist bacteria with more than one ring of DNA?</p>
| [
{
"answer_id": 1091,
"pm_score": 6,
"text": "<p>Vibrio cholerae is known to have two circular chromosomes.</p>\n\n<p>Bacteria cell division is a lot simpler and efficient as compared to eukaryotic cell division, partly due in part to the nature of their chromosomes. They don't have to undergo mitosis --... | [
{
"answer_id": 1092,
"pm_score": 5,
"text": "<p>To expand a little bit the other answer, I would also add that bacteria can have other (usually circular) DNA segments aside from their main chromosome. These are called <a href=\"http://en.wikipedia.org/wiki/Plasmid\" rel=\"nofollow noreferrer\">plasmids<... |
1,101 | <p>Have any experiments been carried out involving sprouting and growing plants in a zero gravity environment? If so, what was the outcome? How did the plants sprout out of the soil without gravity? Did they grow outward or toward light sources?</p>
| [
{
"answer_id": 1102,
"pm_score": 4,
"text": "<p>There have been several experiments in growing plants in <em>microgravity</em> (strictly speaking, we do not achieve \"zero-g\" since astronauts remain in orbit about the Earth).</p>\n\n<p>Changes in plant growth due to the influence of a gravity field is ... | [
{
"answer_id": 1148,
"pm_score": 2,
"text": "<p>I find over 100 articles returned by a PubMed query for \"Arabidopsis microgravity.\" Arabidopsis was taken aboard at least one if not more Space Shuttle missions to answer this and other similar questions. A couple recent papers from this search are:</p>\... |
1,112 | <p>RNA is known to act as an enzyme via its ability to fold itself in specific ways. </p>
<p>Is DNA capable of such structures? Or is it some biochemical reason stopping the folding?
Have they been observed in nature?</p>
| [
{
"answer_id": 1123,
"pm_score": 4,
"text": "<p>There are no known natural DNA enzymes (deoxyribozymes), but there are various synthetic DNA enzymes. The first deoxyribozyme that has been reported (<a href=\"http://www.ncbi.nlm.nih.gov/pubmed/9383394\" rel=\"nofollow\">Breaker and Joyce, 1994</a>) catal... | [
{
"answer_id": 1117,
"pm_score": 2,
"text": "<p>DNA has recently been designed to act as a targeted drug-delivery agent at George Church's lab. This doesn't involve catalyzing a reaction between two substrates, but it does involve significant internal conformational changes based on binding to highly s... |
1,115 | <p>If I were to graft two apple saplings together -- by bending the tops toward each other and lashing them together -- will the plants grow as one and benefit from one another, or will they be fighting each other for root space and light? If they would grow with each other, then I could theoretically grow a line of closely spaced fruit trees to any length, and they would be strengthened by each other in bad conditions. </p>
| [
{
"answer_id": 2500,
"pm_score": 4,
"text": "<p>There are a couple of answers to this question. Especially where trees are concerned, you can graft <a href=\"http://inventorspot.com/articles/lemon_tree_japan_bears_eleven_ki_9572\" rel=\"noreferrer\">two or more trees onto the same rootstock, or even a ... | [
{
"answer_id": 68314,
"pm_score": 2,
"text": "<p>What you describe is not grafting it is called <a href=\"https://en.wikipedia.org/wiki/Inosculation\" rel=\"nofollow noreferrer\">inosculation</a> and can prodice some truly impressive results.\nInosculation can sometimes <em>lead</em> to natural grafting... |
1,129 | <p>Based on pictures, it seems to me that a vast majority of fish species that have scales do NOT have scales on their heads.</p>
<p><strong>Is that fact true?</strong> </p>
<p>To make this properly answerable:</p>
<ul>
<li><p>lets' define a "majority" as >70% of fish species. But frankly, I'm more interested in actual numerical answer than whether it passes some arbitrary threshold or not.</p></li>
<li><p>The universe which I'm interested in measuring the percentage are fish species that have "normal" (Cycloid and ctenoid is the technical term, I believe?) scales on their bodies.</p>
<p>If that's not specific enough, you can restrict the universe to species in Actinopterygii (ray-finned) that have scales.</p></li>
</ul>
| [
{
"answer_id": 71895,
"pm_score": 3,
"text": "<p>I certainly agree with your general observation, but not being an ichthyologist, I can only offer a partial answer, based on a particular family of fish. Within the family <a href=\"https://en.m.wikipedia.org/wiki/Threefin_blenny\" rel=\"nofollow noreferr... | [
{
"answer_id": 71841,
"pm_score": -1,
"text": "<p>Based on a lack of written evidence, in searching Google and Google Scholar, I believe fish have scales on their heads, where I'm defining 'scales' as 'solid, protective bony scales' [see below], and I'm assuming the fish heads are covered with solid pro... |
1,136 | <p>Is there a technical/scientific term that scientists use to refer to tool making abilities found in certain types of animals?</p>
<p>Reference <a href="http://en.wikipedia.org/wiki/Animal_cognition#Tool_and_weapon_use">http://en.wikipedia.org/wiki/Animal_cognition#Tool_and_weapon_use</a></p>
| [
{
"answer_id": 1169,
"pm_score": 4,
"text": "<p>Having read <a href=\"http://www.eva.mpg.de/primat/staff/boesch/pdf/fol_prim_tool_use_making.pdf\">this article</a> on tool use in Chimpanzees in full, I am inclined to say that if such a term existed then either the article itself or the titles of any of ... | [
{
"answer_id": 7301,
"pm_score": 2,
"text": "<p>I think <strong>\"tool use\"</strong> could serve as a good term on it's own, don't you think?</p>\n"
}
] |
1,152 | <p>The field seems extremely divided on the debate. On one hand, artificial experiments have suggested that synonymous mutations don't correlate with gene expression but rather, the mRNA 5' structure is the most important <a href="http://www.ncbi.nlm.nih.gov/pubmed/19359587">1</a>. On the other hand, genome wide analysis suggests that tRNA biases are better associated with high expression <a href="http://www.ncbi.nlm.nih.gov/pubmed/20403328">2</a>. What other works balance out this discussion?</p>
<ol>
<li><a href="http://www.ncbi.nlm.nih.gov/pubmed/19359587">Coding-sequence determinants of gene expression in Escherichia coli</a></li>
<li><a href="http://www.pnas.org/content/107/8/3645.short">Translation efficiency is determined by both codon bias and folding energy</a></li>
<li><a href="http://www.ncbi.nlm.nih.gov/pubmed/20403328">An evolutionarily conserved mechanism for controlling the efficiency of protein translation</a></li>
</ol>
| [
{
"answer_id": 1153,
"pm_score": 5,
"text": "<p>This is an excellent question! To my knowledge, there hasn't been a definite answer yet. Recently, I did tons of research on which factors influence protein expression and you should definitely check out the following questions which I asked: </p>\n\n<ol>\... | [
{
"answer_id": 1408,
"pm_score": 2,
"text": "<p>Consider mRNA <em>primary</em> structure in terms of uORFs, upstream open reading frames. These can cause ribosome pausing or slowing and even disassociation from the mRNA.</p>\n\n<p>I agree that a definite answer is not known (+1). For different mRNAs, un... |
1,171 | <p>Could someone point out some relevant papers or resources (an online DB maybe?) describing the density of neurons (or, more in general, of cells) in different areas of the mouse brain?</p>
| [
{
"answer_id": 1187,
"pm_score": 4,
"text": "<p>The newest and most accurate method (far more accurate than older extrapolating/manual counting methods (Stereology) and yielding some surprising results) to estimate number/density of neurons/cells in brains is <strong>Isotropic Fractionator</strong> to m... | [
{
"answer_id": 2773,
"pm_score": 0,
"text": "<p><a href=\"http://onlinelibrary.wiley.com/doi/10.1002/cne.902860404/abstract\" rel=\"nofollow\">This article</a> seems to be at least part of what you're looking for (although I can only access the abstract at the moment). They report that:</p>\n\n<blockquo... |
1,181 | <p>Question originally asked on Quora. These proteins have many functional similarities, so why do cells need both to handle unfolded proteins?</p>
| [
{
"answer_id": 1195,
"pm_score": 3,
"text": "<p>Often cells have multiple types of the same protein — this redundancy can have different effects for different requirements such as having proteins function under different physiological conditions, or providing specificity to a certain class of ligand pro... | [
{
"answer_id": 1200,
"pm_score": 3,
"text": "<p>Hsp70 and Hsp90 are not single proteins, but entire protein families. And those two protein families are not the only ones of their kind. There are different groups of heat shock proteins, Hsp70 and Hsp90 are molecular chaperones that assist in protein fol... |
1,205 | <p>My note about which I am not sure:</p>
<blockquote>
<p>Secondary oocyte is arrested in the metaphase II monthly after puberty until fertilization with sperm. </p>
</blockquote>
<p>The following picture also satisfies my sentence: <img src="https://i.stack.imgur.com/2GFHd.png" alt="enter image description here">.</p>
<p>So you can see that the secondary oocyte that is arrested seems to be Graafian.</p>
<p>I know that Graafian develops during the second week.
I know that the secondary follicle is developing two days before <a href="http://www.embryology.ch/anglais/dbefruchtung/eisprung02.html" rel="nofollow noreferrer">ovulation</a>.
It seems that the development of the secondary follicle ends and the formation of Graafian follicle occurs just before ovulation.
My lecture material suggests that Graafian follicle is arrested in metaphase II, since Graafian follicle is ovulated once in a month and waits sperm in tuba uterina infundibulum:</p>
<p><img src="https://i.stack.imgur.com/3Twn3.png" alt="enter image description here"></p>
<p>The answer to my question is not also clear from <a href="https://biology.stackexchange.com/questions/954/does-human-female-meiosis-ii-occur-after-fertilization-with-sperm">my previous thread</a>:</p>
<blockquote>
<p>An oocyte completes meiosis I as its follicle matures (during ovulation) resulting in a secondary oocyte and the FIRST polar body. After ovulation, each oocyte continues to metaphase of meiosis II.</p>
</blockquote>
<p><strong>Which follicle is arrested in the metaphase II of oogenesis?</strong></p>
| [
{
"answer_id": 1741,
"pm_score": 2,
"text": "<p>Graafian follicle.</p>\n\n<p>The secondary oocyte and thus Graafian follicle are arrested in the second metaphase of oogenesis.\nAfter this the corpus luteum develops from the follicle during the luteal phase of the menstrual cycle.</p>\n"
}
] | [
{
"answer_id": 35159,
"pm_score": 0,
"text": "<p>Three follicular stages are recognised,\n1) Primary/Preantral Follicles (with primary oocyte inside)\n2) Secondary/Antral Follicles (with primary oocyte inside)\n3) Pre Ovulatory Follicles (with secondary oocyte inside)</p>\n\n<p>Pre ovulatory Follicles a... |
1,206 | <p>This thread is related to <a href="https://biology.stackexchange.com/questions/991/what-are-differences-between-formation-of-embryonic-disc-in-chick-and-mammal-emb">my previous thread</a> which is still unsolved mainly. I need to be able to compare chick and human cleavage and blastulation of zygote.
My friend says that</p>
<blockquote>
<p>Chicken have discoblast, human not. That is the main thing to get the idea of the difference.</p>
</blockquote>
<p>I know that chicken have yolk sac with yolk, while human have yolk sac without yolk.</p>
<p>My notes say that</p>
<blockquote>
<p>Cleavage in birds is partial discoidal (embryo forms disc and cells called blastodisc are on top of the yolk). </p>
</blockquote>
<p>So embryo forms some disc, lets call it #1. Some cells called blastodisc are on top of the yolk. <strong>So are the cells called blastodisc on top of the yolk and the disc #1?</strong></p>
<p><strong>What is the name of the given disc that chick embryo forms?</strong>
It seems that human is not forming the given disc. Apparently, the name of the given disc is discoblast, the thing he says is very important.</p>
| [
{
"answer_id": 1284,
"pm_score": 3,
"text": "<p>It is a mnemonic of two words: discoidal + blastula = discoblastula.\nSo it suggests that cleavage is partial discoidal in birds.\nEmbryo forms disc. \nCells called blastodisc are on top of the yolk.\nIt seems that the formed disc is blastodisc.</p>\n"
}... | [
{
"answer_id": 71002,
"pm_score": 0,
"text": "<p>The cleavage in birds is restricted to the blastodisc lying on the top of the yolk towards the animal pole of the zygote, this type of cleavage is termed as discodial cleavage because the embryo forms disc and cells that are also on the top of the yolk.</... |
1,224 | <p>Say I have one dsDNA that undergoes normal PCR (where amplification is exponential). If there is a mistake, say a G is swapped for an A during the 2nd round of replication, what percentage of the final DNA will have the mistake if there are 12 more rounds? </p>
<p>I was talking to my teacher about this today. I say 33%, my teacher said 12.5%.</p>
| [
{
"answer_id": 1227,
"pm_score": 4,
"text": "<p>I will format it to .ppt as soon as I have more time! If something is not readable, please let me know!</p>\n\n<p>I have to point out several things:</p>\n\n<ol>\n<li><p>The fraction of incorrect DNA molecules does not depend on the number of cycles (as lo... | [
{
"answer_id": 1226,
"pm_score": 3,
"text": "<p>Your teacher is indeed correct.</p>\n\n<p>In the first round you would get two identical molecules of the dsDNA.</p>\n\n<p>In the second round you would get 3 identical molecules and one molecular with an <code>A</code> substituted for a <code>G</code> in ... |
1,254 | <p>I'm looking to generation sequential deletions from a gene of interest. The total size of this region is 8 amino acids. I'm trying to determine which portion of this region is necessary within the gene.</p>
<p>For example, if this is my sequence:
<br />
ABCDEFGH</p>
<p>I want to generate:
<br />
BCDEFGH, CDEFGH, DEFGH, and so on.</p>
<p>What is the least expensive way to do this (by minimizing primer use, enzyme use, etc). I already have this gene sub-cloned into an expression vector.</p>
<p>Thanks!</p>
| [
{
"answer_id": 1255,
"pm_score": 4,
"text": "<p>While it isn't the cheapest, it is certainly the fastest and simplest. I would quikchange out the amino acid. This would require no subcloning and only require </p>\n\n<ul>\n<li>two ~25 nt primers ($10)</li>\n<li>1 shot of pfu (~$0.25)</li>\n<li>1 shot of ... | [
{
"answer_id": 1258,
"pm_score": 3,
"text": "<p>Deletions may make sense if you are analyzing the N-terminus or C-terminus of a protein. If you are looking at an internal region however, keep in mind that the more AAs you delete, the more likely you are to disrupt the overall protein structure. If you d... |
1,259 | <p>I have a relatively simply gene regulatory network I would like to visualize, complete with the common arrow and bar symbols used to show, respectively, which genes enhance or repress with other genes. Is there a way to typeset a gene regulatory network using something like LaTeX or Graphviz? </p>
<p>For very simple networks, I guess something like Photoshop or Illustrator would probably be the quickest solution, but these programs become very tedious as the size of the network grows even a little bit. What do people typically use for this type of task?</p>
| [
{
"answer_id": 1260,
"pm_score": 4,
"text": "<p>If you have simple 1:1 connections or can list your data in that manner, you can try Cytoscape (freely available). There are numerous plug-ins to customize what you have in mind in terms of visualization.</p>\n"
}
] | [
{
"answer_id": 1263,
"pm_score": 2,
"text": "<p>I haven't tried it, but this <a href=\"https://stackoverflow.com/questions/2278030/improving-graphviz-layout\">StackOverflow answer</a> suggests that you can import a GraphViz network into <a href=\"http://www.omnigroup.com/products/omnigraffle/\" rel=\"no... |
1,264 | <p>I am investigating the strength of binding of a small peptide to a protein by isolating the bound version and subjecting it to collisions with gas molecules (CID mass spectrometry) to dissociate the complex.
When I plot the collision energy against the proportion of bound and unbound proteins I get a curve that looks like a K<sub>d</sub> curve. However, as the interaction isn't in equilibria (i.e. it is in the gas phase) calculating the K<sub>d</sub> value wouldn't be correct. </p>
<p>So is there another value I could calculate to describe the strength of the interaction?</p>
| [
{
"answer_id": 1292,
"pm_score": 3,
"text": "<p>Bobthejoe was pointing in the right direction kcat and Km - Michaelis Menton parameters are measured to look at the relative rates of an enzyme in non equilibrium state. Basically kcat is 'how fast does the enzyme work with little or no product in soluti... | [
{
"answer_id": 1274,
"pm_score": 3,
"text": "<p>You should be looking at the interactions in terms of kinetics and not thermodynamics. k_on and k_off should do the trick.</p>\n"
}
] |
1,280 | <p>Recently I've been studying the p53 tumor suppressor gene as a model for regulation of gene expression. It's amazing how many different post-translational modifications are known to regulate p53 activity, and how many different factors are involved in this regulation.</p>
<p>It is postulated that there are between 20,000 and 30,000 genes in the human genome. Is there an estimate for the percentage of these genes whose primary function is related to regulation of gene expression?</p>
| [
{
"answer_id": 1287,
"pm_score": 4,
"text": "<p>Okay, I'll take this out of the comments and put in an answer for all of us to work on. </p>\n\n<p>To directly answer your question: </p>\n\n<blockquote>\n <p>\"Is there an estimate for the percentage of these genes whose primary\n function is related to... | [
{
"answer_id": 1283,
"pm_score": 3,
"text": "<p>Yes, look at FANTOM and their work. There are about 2000 transcription factors and co-factors in the human genome. These are proteins, of course. If you add a couple (or few?) thousand microRNAs and a few dozen anti-sense transcripts, although small in siz... |
1,326 | <p>A friend of mine told me an anecdote about his mother, who drank too much caffeine, to the point she became hypotensive and would pass out. Because caffeine acts as a stimulant, I'm assuming the decreased blood pressure was some kind of tolerance effect.</p>
<p>How exactly would caffeine have disrupted her circulatory regulation and caused her normal pressure to decrease?</p>
| [
{
"answer_id": 1327,
"pm_score": 4,
"text": "<p>I can't speak to the causes of hypotension, but you are indeed correct, caffeine is a stimulant. As a stimulant, there is a well documented acute period of <em>hypertension</em> that lasts for up to 4 hours. Interestingly, there is no causal link establish... | [
{
"answer_id": 100624,
"pm_score": 0,
"text": "<p>Caffeine's mechanism of action,, Hindawi journal (<a href=\"https://www.hindawi.com/journals/ijvm/2010/834060/\" rel=\"nofollow noreferrer\">https://www.hindawi.com/journals/ijvm/2010/834060/</a>)</p>\n<p>Direct effects of caffeine:\nOn vascular smooth m... |
1,328 | <p>I'm working with luciferase and I want to be able to take a photo of it. The trouble is, I can see the luciferase glowing in all of its glory in front of me but no matter how hard I try, I can't take a photo of the luciferase with my DSLR (Nikon D80).</p>
<p>I'm curious if I'm missing a certain lens or if I should be shooting using a different lighting setup. I'm already exposing for 30". Perhaps longer?</p>
| [
{
"answer_id": 1333,
"pm_score": 3,
"text": "<p>You'll also want to make sure that you are imaging in complete darkness because you may have very low photon emission from your luciferase system and any amount of background light can overwhelm your signal with noise.</p>\n"
}
] | [
{
"answer_id": 1332,
"pm_score": 3,
"text": "<p>You are looking for a <a href=\"http://www.google.com/cse?cx=004738989115247203233:09r2ltc-nlc&ie=UTF-8&q=luciferase#gsc.tab=0&gsc.q=bioluminescence%20imaging\">bioluminescence imaging device</a>. These have very sensitive CCD camera and exposu... |
1,339 | <p>Do ants even breathe? If they don't, how do they stay alive? On what resources do they depend upon to stay alive? How are they different form mammals?</p>
| [
{
"answer_id": 1340,
"pm_score": 4,
"text": "<p><a href=\"http://www.google.com/url?sa=t&rct=j&q=how%20do%20insects%20breathe&source=web&cd=4&ved=0CFEQFjAD&url=http://www.new-ecopsychology.org/en/insects/pages/p-8.htm&ei=6hpYT_rDEYPx0gGIpPmaDw&usg=AFQjCNHtfR2N6y7ig3tjv4Rz... | [
{
"answer_id": 2770,
"pm_score": 3,
"text": "<p>The main difference between tracheal gas exchange, and other forms of gas exchange (except simple diffusion) is that it is generally a passive process. Organisms with lungs, gills, or other modified respiratory organs can actively pump the oxygen-containin... |
1,362 | <p>Why is blood pressure generally higher in more distal arteries?</p>
<p><img src="https://i.stack.imgur.com/4qSMQ.png" alt=""></p>
| [
{
"answer_id": 7167,
"pm_score": 4,
"text": "<p>Because of reflected pressure waves and the stiffness of the blood vessel. The forward pressure wave from the heart travels much faster than the blood itself and is reflected at areas of tapering and branching. This backward wave slows the forward flow o... | [
{
"answer_id": 1381,
"pm_score": 2,
"text": "<p>The cardiovascular system is affected by three types of pressure. These are:</p>\n\n<ul>\n<li><strong>Heamodynamic</strong> - caused by the contraction of the heart, which would give the view of pressure being higher closer to the aorta as in Kevin's answ... |
1,415 | <p>In some white caladiums, there is less than a square inch of green space spread over the whole leaf. How do these plants perform the photosynthesis necessary to support the large leaves, the roots, the flowers, and build a corm?</p>
<p><img src="https://i.stack.imgur.com/k6Bgs.jpg" alt="enter image description here"></p>
| [
{
"answer_id": 9381,
"pm_score": 4,
"text": "<p>There are many different kinds of plants that have independently evolved this sort of variegation (non-green areas) in the leaves. However, the mechanisms by which they effect this vary between species.</p>\n\n<p>Some have little or no chlorophyll in the n... | [
{
"answer_id": 1423,
"pm_score": 2,
"text": "<p>Any free growing (non parasitic) plant will rely on photosynthesis. </p>\n\n<p>Plants do not have to be green though. It says in <a href=\"http://www.google.com/url?sa=t&rct=j&q=university%20of%20florida%20news%20white%20caladiums&source=web&am... |
1,435 | <p>So, as far as I understand (basic) evolutionary theories, diversity is generated by "niching." That is, if there is an environmental factor that hasn't been fully used by any species to "profit" off, there will be a tendency to fill up that "niche" and thus speciation occurs (not in one day of course).</p>
<p>I was standing in the kitchen earlier and was wondering: what is the niche that an apple fills in respect to a pear end vice versa? If I'm not mistaken they are form the same family and thus share a common ancestor (albeit I don't know if it is a "recent" ancestor). </p>
<p>Is it a geographical thing or do they genuinely vie for the same thing in a different way? (e.g. a pear aims to be eaten by animals that have small teeth and thus want a softer fruit, while an apple aims to be eaten by the bigger animals, that like a heartier bite).</p>
<p><em>note: I know that this question might be too speculative and too localised to be any good, but hey, some of you might just know this!</em></p>
| [
{
"answer_id": 1438,
"pm_score": 4,
"text": "<p>The ancestral apple is thought to originate in what is now Kazakhstan. See this <a href=\"http://www.ars.usda.gov/is/AR/archive/jan06/apples0106.htm\">report</a> from the USDA on this topic. Those early apples were small and likely eaten more often by non-... | [
{
"answer_id": 1437,
"pm_score": 4,
"text": "<p>I wouldn't be suprised if no one has hard data on this. In any case there is more than one answer to this question. </p>\n\n<p><a href=\"http://en.wikipedia.org/wiki/Ecological_niche\" rel=\"nofollow noreferrer\">Niches</a> are defined more than one way. <... |
1,442 | <p>Some protocols call for fluid samples to be mixed with a "vortexer" on the high setting. What effect does the vortexing have on fluid samples that mechanical shaking does not? Does it shear long molecules like DNA, for instance?</p>
<p>A friend is setting up a new lab and asked if vortexers were strictly necessary. I am aware they are often called for in various protocols, but I actually don't know what specific effect the vortexing has that makes it better than manual shaking. What do you think?</p>
<p><img src="https://i.stack.imgur.com/rI9yD.jpg" alt="A typical lab vortexer"> </p>
| [
{
"answer_id": 1443,
"pm_score": 5,
"text": "<p>In my experience, shaking and mixing have different \"dead spaces\". Supposed you had an eppendorf tube and you stirred it around with a pipet tip for thirty minutes. You would have great convective mixing in the radial direction but virtually no mixing in... | [
{
"answer_id": 1453,
"pm_score": 4,
"text": "<blockquote>\n <p>what specific effect the vortexing has that makes it better than manual shaking</p>\n</blockquote>\n\n<p>In addition to @bobthejoe's answer about viscous fluids, (manual) mechanical shaking is also less consistent and more tiresome than vor... |
1,445 | <p>Is there any relation between age and the frequency of flatus? I often have this feeling that older people f*** more often than younger ones. Is this feeling scientifically correct? </p>
| [
{
"answer_id": 1460,
"pm_score": 3,
"text": "<p>I do not have access to journals, but there is <a href=\"http://www.ncbi.nlm.nih.gov/pubmed/8769291\" rel=\"nofollow\">this paper</a> claiming in its abstract that age DOES NOT play a role in flatus frequency.</p>\n\n<p>Reference: <a href=\"http://www.ncbi... | [
{
"answer_id": 1450,
"pm_score": 2,
"text": "<p>Could be that age has an effect. As humans age three important factors, with respect to this question, change:</p>\n\n<ol>\n<li><p>Diet.</p></li>\n<li><p>Immune system flexibility and its response to even minor disturbances and infections.</p></li>\n<li><p... |
1,452 | <p>According to my lecture notes testosterone generally increases sexual behavior.
Given that it's generally thought to be the male hormone I'm not quite sure whether they mean that it also increases sexual behavior in females.</p>
<p>What is the effect of testosterone on female sexual behavior?</p>
| [
{
"answer_id": 1455,
"pm_score": 5,
"text": "<p>I'll point you to this article by <a href=\"http://dx.doi.org/10.1001/archpsyc.57.2.149\" rel=\"nofollow\">A. Tuiten et al</a>.</p>\n\n<p>To quickly answer your question, yes, <strong>testosterone does have an enhancing effect on the sexual behaviour of h... | [
{
"answer_id": 1456,
"pm_score": 3,
"text": "<p>Although male testes are responsible for huge testosterone secretion, testosterone can be produced by other organs both in males and females. So, women do have testosterone. Similarly, estrogen is also produced in men and not only in women. In addition, b... |
1,462 | <p>According to <a href="http://en.wikipedia.org/wiki/Swan">the Wikipedia article on swans</a>, swans are mostly monogamous but may sometimes separate, particularly after a "nesting failure". What "nesting failure" may mean is not entirely clear to me. Does it mean that they they have literally failed to build a physical nest? Or is it that they have failed to produce offspring? Or is it something else entirely?</p>
| [
{
"answer_id": 1463,
"pm_score": 4,
"text": "<p>Apparently it refers to the inability of nesting the eggs, because the nest was somehow destroyed, or environmental conditions were unfavourable.</p>\n\n<p>I found a few examples pointing in this direction:</p>\n\n<p>The Trumpeter Swan page on the <a href=... | [
{
"answer_id": 1464,
"pm_score": 3,
"text": "<p>Actually, nesting failure means that nesting trial fail before offspring could even leave the nest. In case of precocial species (where chicks leave nest immediately after hatching, like swans) it means that eggs was destroyed or parents abandoned nest, as... |
1,470 | <p>Some insects, like the crickets pictured below, have such slender antennae it seems no blood could fit. How do they get blood through their antennae?</p>
<p><img src="https://i.stack.imgur.com/DMeVR.jpg" alt="enter image description here"><img src="https://i.stack.imgur.com/r37ZV.jpg" alt="enter image description here"></p>
| [
{
"answer_id": 9829,
"pm_score": 3,
"text": "<p>Insects do not posses closed circulatory system, but a space where organs float in a fluid called hemolymph. They don't have blood vessels (but some arthropodes have pumps that act a like heart). The hemolymph allows nutrients and excretion products to dif... | [
{
"answer_id": 1474,
"pm_score": 3,
"text": "<p>Insects primarily get oxygen through diffusion of air through their skin. I doubt the antennae need hemolymph circulation. </p>\n"
}
] |
1,483 | <p>I understand that many protein DNA binding domains bind to DNA via basic residues such as Arginine and Lysine. But what is the mechanism used to bind to DNA and where on the DNA would these residues bind? </p>
| [
{
"answer_id": 1493,
"pm_score": 4,
"text": "<p>This question has no particular answer. There are several families of DNA binding proteins, some of them bind specifically (e.g. restriction enzymes like EcoRI which binds to and cuts GAATTC or transcription factors like <a href=\"http://users.rcn.com/jki... | [
{
"answer_id": 13635,
"pm_score": 0,
"text": "<p>I'd make a comment if I could, but our lab has worked with a lot of poly lysine peptides for binding DNA. In our experience, lysine works better than arginine, and both work a lot better than histidine. Histidine has a lower pka, so it tends to be less po... |
1,542 | <p>I understand that it's feasible the bacteria within the gastrointestinal tract originate from the food we eat and air we breath, but where does this population of microbes originate from?</p>
| [
{
"answer_id": 1546,
"pm_score": 5,
"text": "<p>Most of the initial colonisation is said to be coincidental ('happenstance' as the textbook puts it!) exposure. </p>\n\n<p>It's then fairly predictable depending on:</p>\n\n<ul>\n<li>type of delivery (as Larry commented);</li>\n<li>feeding; and</li>\n<li>r... | [
{
"answer_id": 1543,
"pm_score": 2,
"text": "<p>There is some interesting information <a href=\"http://www.hmpdacc.org/impacts_health/impact_health.php\" rel=\"nofollow\">here</a> from the Human Microbiome Project, but no details regarding the source of vaginal microflora. I would say that the sources w... |
1,556 | <p>I'm sure that everyone is familiar with the sensation commonly known as "butterflies in the stomach". It is commonly experienced during periods of anxiety or stress (e.g. before high stakes job interviews or roller coaster rides) and apparently (after my web research) often felt in new romances without an obvious cause of tension. </p>
<p>However, whilst my googling did turn up an inordinate amount of rubbish regarding love-sicknesnes, I have been unable to find even a suggestion as to a mechanism as to the physiology behind this feeling. Is it a sensation of physical change in the stomach (some sites vaguely mentioned the restriction of blood flow to critical organs but it was entirely unsupported) or is it neurological in nature? </p>
| [
{
"answer_id": 1561,
"pm_score": 5,
"text": "<p>If you want to find out about the the relationship of this response to romance in particular, there's a pretty comprehensive research paper called <em>Love is more than just a kiss: a neurobiological perspective on love and affection</em>[1] which reviews ... | [
{
"answer_id": 1557,
"pm_score": 3,
"text": "<p>Nervousness or excitement should cause an increase in activity in the sympathetic nervous system (the so-called \"fight or flight\" side of the autonomic system). Increased sympathetic activity will be associated with decreased parasympathetic activity (pr... |
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