Sentence stringlengths 158 2.09k | video_title stringlengths 11 104 |
|---|---|
So the front of the box is 20 centimeters tall and 10 centimeters wide. It's a rectangle, so to figure out its area, we can just multiply 20 centimeters times 10 centimeters and that's going to give us 200 centimeters. 200 square centimeters, I should say. 200 square centimeters, that's the area of the front. Let me wr... | Surface area of a box.mp3 |
200 square centimeters, that's the area of the front. Let me write it over here as well, 200. Now, we also know there's another side that has the exact same area as the front of the box and that's the back of the box. So let's write another 200 square centimeters for the back of the box. Now let's figure out the area o... | Surface area of a box.mp3 |
So let's write another 200 square centimeters for the back of the box. Now let's figure out the area of the top of the box. The top of the box is, we see the box is 3 centimeters deep. So this right over here is 3 centimeters. It's 3 centimeters deep and it's 10 centimeters wide. We see the box is 10 centimeters wide. ... | Surface area of a box.mp3 |
So this right over here is 3 centimeters. It's 3 centimeters deep and it's 10 centimeters wide. We see the box is 10 centimeters wide. So the top of the box is going to be 3 centimeters times 10 centimeters, which is 30 square centimeters of area. So that's the top of the box, 30 square centimeters. Well, the bottom of... | Surface area of a box.mp3 |
So the top of the box is going to be 3 centimeters times 10 centimeters, which is 30 square centimeters of area. So that's the top of the box, 30 square centimeters. Well, the bottom of the box is going to have the exact same area. We just can't see it right now, so that's going to be another 30. And we have two more s... | Surface area of a box.mp3 |
We just can't see it right now, so that's going to be another 30. And we have two more sides because this box has six sides. We have this side panel that is 20 centimeters tall. We see that the height of the box is 20 centimeters. And 3 centimeters deep. So 3 times 20, 3 times 20, that's 20 centimeters right there. 3 c... | Surface area of a box.mp3 |
We see that the height of the box is 20 centimeters. And 3 centimeters deep. So 3 times 20, 3 times 20, that's 20 centimeters right there. 3 centimeters times 20 centimeters is going to give us 60 square centimeters. Now that's this side panel, but there's another side panel that has the exact same area that's on the o... | Surface area of a box.mp3 |
What I want to do in this video is give ourselves a quick overview of the different ways that cells can communicate with each other. And maybe the most basic one is just through direct contact. Direct contact. And this can happen several different ways. One way could be you just have neighboring cells. So this is one c... | Overview of cell signaling.mp3 |
And this can happen several different ways. One way could be you just have neighboring cells. So this is one cell right over here. And this is the neighboring cell right over here. And they actually might have gaps in their membranes. If these are plant cells, we would call these gaps gap junctions. So you might have t... | Overview of cell signaling.mp3 |
And this is the neighboring cell right over here. And they actually might have gaps in their membranes. If these are plant cells, we would call these gaps gap junctions. So you might have the, I just drew two of them. And this is obviously just kind of a two-dimensional slice. So we're not fully appreciating the three-... | Overview of cell signaling.mp3 |
So you might have the, I just drew two of them. And this is obviously just kind of a two-dimensional slice. So we're not fully appreciating the three-dimensional structure. But the basic idea is maybe the cell on the left starts producing some molecules, especially some small molecules that are able to go through these... | Overview of cell signaling.mp3 |
But the basic idea is maybe the cell on the left starts producing some molecules, especially some small molecules that are able to go through these gap junctions. And when they're able to go through the gap junctions, maybe they latch on to some proteins in the second cell that start maybe activating them in a certain ... | Overview of cell signaling.mp3 |
So this would be a form of communication. Something happened in this first cell to produce these molecules. Those molecules were able to get into the second cell and trigger a response. And as I mentioned, if these are animal cells, we would call these gaps, we'd call them gap junctions. So that right over there, that ... | Overview of cell signaling.mp3 |
And as I mentioned, if these are animal cells, we would call these gaps, we'd call them gap junctions. So that right over there, that is a gap junction. And we cover this in other videos. And if we're talking about plant cells, we can have very similar things happening, but we wouldn't call them gap junctions. These wo... | Overview of cell signaling.mp3 |
And if we're talking about plant cells, we can have very similar things happening, but we wouldn't call them gap junctions. These would be gaps not just through the, not even tunnels through the membrane. It would also be through the cell walls. If we're talking about plants, they would be plasmodesmata. Plasmodesmata.... | Overview of cell signaling.mp3 |
If we're talking about plants, they would be plasmodesmata. Plasmodesmata. And we talk about these more in the structure of cell videos. But there's other ways that you could communicate via direct contact. You could imagine maybe some cells that are floating around in the bloodstream. Maybe this is one cell over here.... | Overview of cell signaling.mp3 |
But there's other ways that you could communicate via direct contact. You could imagine maybe some cells that are floating around in the bloodstream. Maybe this is one cell over here. Maybe this is another cell over here. And they have complementary surface proteins, surface proteins that are able to bind to each other... | Overview of cell signaling.mp3 |
Maybe this is another cell over here. And they have complementary surface proteins, surface proteins that are able to bind to each other. So maybe this one has a surface protein that looks like this. I'm obviously exaggerating its shape. The protein would look exactly like this inverted triangle. But this one has a sur... | Overview of cell signaling.mp3 |
I'm obviously exaggerating its shape. The protein would look exactly like this inverted triangle. But this one has a surface protein like this, and I'm also exaggerating its size relative to its cell just so we can appreciate how they could maybe lock together. So this one has a surface protein like that. And when they... | Overview of cell signaling.mp3 |
So this one has a surface protein like that. And when they bind to each other, it might change the proteins in some way and then trigger a reaction in each of these cells. The communication then continues. If this protein changes a little bit, it might activate something. It might activate the release of some molecules... | Overview of cell signaling.mp3 |
If this protein changes a little bit, it might activate something. It might activate the release of some molecules, might activate some other proteins, might catalyze some type of reaction. We've seen this in multiple other videos. All sorts of crazy biological reactions could happen inside of cells. But it might elici... | Overview of cell signaling.mp3 |
All sorts of crazy biological reactions could happen inside of cells. But it might elicit a, it could elicit a response. And actually it could even elicit a response in both cells. Some type of response. They know that they are latched on. They know that they are latched on to someone else. Now direct contact, you coul... | Overview of cell signaling.mp3 |
Some type of response. They know that they are latched on. They know that they are latched on to someone else. Now direct contact, you could imagine, is not the only way that you could have cell-cell signaling. You could actually have cells start to signal over a little bit of a distance by releasing molecules into the... | Overview of cell signaling.mp3 |
Now direct contact, you could imagine, is not the only way that you could have cell-cell signaling. You could actually have cells start to signal over a little bit of a distance by releasing molecules into the extracellular space and eventually even into the bloodstream. So for example, let me draw a cell. A cell right... | Overview of cell signaling.mp3 |
A cell right over here. And maybe it's able to produce some molecules. And these molecules, either, they might be lipid soluble and maybe make their way through the cellular membrane on their own, or maybe they are packed in nice vesicles that allow them to traverse the membrane. So when you get actually, so the membra... | Overview of cell signaling.mp3 |
So when you get actually, so the membrane of the vesicle merges with the membrane of the cell. And then it allows these things to get out. And so you can imagine, if another cell has the right receptors for these, that would signal some type of a response, or it will form some form of communication. So let's say that I... | Overview of cell signaling.mp3 |
So let's say that I have, actually let me draw a couple of cells. So let's say I have this cell over here. And then I have this cell over here. And let's say that this cell has the right receptor. Has the right receptor. And this cell doesn't. It could have other receptors. | Overview of cell signaling.mp3 |
And let's say that this cell has the right receptor. Has the right receptor. And this cell doesn't. It could have other receptors. Maybe it has receptors like that. But it's not the right receptor. And so these molecules that were released by this first cell could bind, not on this character, not on this protein, this ... | Overview of cell signaling.mp3 |
It could have other receptors. Maybe it has receptors like that. But it's not the right receptor. And so these molecules that were released by this first cell could bind, not on this character, not on this protein, this surface protein, but it could bind on this character. So it could bind on this character. And when i... | Overview of cell signaling.mp3 |
And so these molecules that were released by this first cell could bind, not on this character, not on this protein, this surface protein, but it could bind on this character. So it could bind on this character. And when it does so, this protein that's on the cellular membrane, it might change its shape, it might do al... | Overview of cell signaling.mp3 |
And we'll go into more detail in future videos on exactly how that happens, or what these responses actually might be. Now, if this is over a short distance, if this is over, if this is a short distance, short, if this is a short distance, short distance, we would call this paracrine. This would be part of the paracrin... | Overview of cell signaling.mp3 |
Let me write that down. Paracrine, paracrine system, or paracrine communication, or paracrine signaling. And we would call these paracrine factors. But if it was happening over long distances, say maybe these molecules, they enter into the bloodstream, so they make their way into the bloodstream right over here. So let... | Overview of cell signaling.mp3 |
But if it was happening over long distances, say maybe these molecules, they enter into the bloodstream, so they make their way into the bloodstream right over here. So let me depict somehow that this is the bloodstream. So this is the bloodstream, bloodstream, and they're able to make, and they're able to go through t... | Overview of cell signaling.mp3 |
So maybe this one has the right receptors for those, for those, for those molecules. Then we call this endocrine system, or this is endocrine signaling. So long distances, long, long distances, we would call this the endocrine system, or endocrine, endocrine signaling, endocrine signaling. And we're talking about the e... | Overview of cell signaling.mp3 |
And we're talking about the endocrine system and endocrine signaling. These molecules, which could just be, you know, they could be all sorts of different types of molecules. They could be steroids. They could be proteins of some kind. We call, in this case, we would call them hormones. You've probably heard the word b... | Overview of cell signaling.mp3 |
They could be proteins of some kind. We call, in this case, we would call them hormones. You've probably heard the word before, and we will do a whole series of videos on hormones. But these molecules actually can even affect the cell that produced them. For example, the cell that produced it might have the right recep... | Overview of cell signaling.mp3 |
But these molecules actually can even affect the cell that produced them. For example, the cell that produced it might have the right receptor, might have the right receptor. And so if it's able to signal, if it's able to trigger a reaction in itself, so if these things are able to trigger a reaction in itself, we woul... | Overview of cell signaling.mp3 |
Autocrine. It is acting on itself. And just so you're familiar with some of the terminology, these proteins on the surface, and this would be the case especially if you have a, if you have non-lipid soluble types of signaling factors or molecules right over here, these proteins, well, actually even if they're on the su... | Overview of cell signaling.mp3 |
So that right over there, that is a receptor. Receptor. And the molecules themselves, these things that bind onto the receptor, we call them the ligand. Ligand in general is a general term for something that binds onto a receptor. And so at that point where you bind onto a receptor, whether you're talking about the par... | Overview of cell signaling.mp3 |
Ligand in general is a general term for something that binds onto a receptor. And so at that point where you bind onto a receptor, whether you're talking about the paracrine process or endocrine, endo, actually endo, I left a C out here, endocrine signaling, this process where it kind of starts to, where it latches on,... | Overview of cell signaling.mp3 |
And we could leave it at that. We could all go home because we're done. But that's not going to make much of a video. What we really want to ask ourselves is, what is that? What is evolution? And how does it result in biodiversity? I like to think of the study of evolution as following two fairly simple pathways. | Biodiversity and natural selection.mp3 |
What we really want to ask ourselves is, what is that? What is evolution? And how does it result in biodiversity? I like to think of the study of evolution as following two fairly simple pathways. These paths are pattern and process. Both of these are not only fascinating areas of study, but are crucial in expanding ou... | Biodiversity and natural selection.mp3 |
I like to think of the study of evolution as following two fairly simple pathways. These paths are pattern and process. Both of these are not only fascinating areas of study, but are crucial in expanding our knowledge of how life originated and how it continues to evolve. The pattern pathway studies the shape of evolut... | Biodiversity and natural selection.mp3 |
The pattern pathway studies the shape of evolution itself by looking at relationships, relationships among organisms over time. And to do that, you need to create a diagram or structure that links these organisms in time, showing a branching sequence of relationships, much like a family tree or genealogy. These evoluti... | Biodiversity and natural selection.mp3 |
Organisms depicted by genealogical trees really are a subject all on their own called phylogenetic systematics. But let's set that aside for a moment. The process path is maybe a slightly better way to start. We want to talk about the mechanisms of evolution, how it actually happens. These are the drivers of the divers... | Biodiversity and natural selection.mp3 |
We want to talk about the mechanisms of evolution, how it actually happens. These are the drivers of the diversity along the multitude of lineages that spring out, branching and branching up the tree, up the limbs of the tree of life. Darwin and even some of his predecessors understood this. They could see that things ... | Biodiversity and natural selection.mp3 |
They could see that things could change, that the pattern of life, this tree, existed, that evolution happened, and that the relationships among organisms could be traced by looking at features of those organisms and how they changed depending on where they were in the tree. They could see, for example, that the wings ... | Biodiversity and natural selection.mp3 |
But at the same time, you could have change among the branches within those lineages. You could get a change in the front leg to a wing or to a grasping arm. General patterns were evident in everything. But at the time, there wasn't a good understanding of the mechanisms, the processes that could explain how these obvi... | Biodiversity and natural selection.mp3 |
But at the time, there wasn't a good understanding of the mechanisms, the processes that could explain how these obviously changing, yet related forms could come about. Darwin and his contemporaries read a lot of stuff about variation, which was visible all around them. It could all be seen. They realized that not all ... | Biodiversity and natural selection.mp3 |
They realized that not all the individuals in a species or even in a population were exact duplicates of each other. This was a surprise to some people, but the evidence was everywhere, even in things as simple as the speed of racehorses. If you didn't have variation in how fast horses could run, the races would be pre... | Biodiversity and natural selection.mp3 |
Races actually demonstrate how horses were chosen for variations in speed. Humans bred fast horses with each other to get even faster horses. And these horses were selected for being the fastest. And that's the key word, selection. Darwin thought, hey, what if nature worked that way? What if nature selected organisms s... | Biodiversity and natural selection.mp3 |
And that's the key word, selection. Darwin thought, hey, what if nature worked that way? What if nature selected organisms somehow? He noticed that the form and the physiology and the behavior of plants and animals varied within natural populations just as much as they did in domesticated populations of things like hor... | Biodiversity and natural selection.mp3 |
He noticed that the form and the physiology and the behavior of plants and animals varied within natural populations just as much as they did in domesticated populations of things like horses. Darwin realized that what we're really talking about here are the beginnings of the understanding of the evolutionary mechanism... | Biodiversity and natural selection.mp3 |
Better, that is, at gathering food, staying away from predators, turning sunlight into usable energy, resisting wind, having good root systems. In other words, fitting the circumstances of the environment and surviving. What Darwin was really saying is that fitness of an individual meant being better able to produce of... | Biodiversity and natural selection.mp3 |
This has been referred to as survival of the fittest. Actually, I prefer the phrase survival of the fitter because fittest implies that there's an endpoint, that there's a goal, but there isn't. It's all relative because there are so many compromises and trade-offs in being well suited to a place as complex as the natu... | Biodiversity and natural selection.mp3 |
This process of the environment selecting variants that are better suited to that environment, no matter how complex, is called natural selection. And those traits that make the selected variants better able to survive and reproduce and pass on those traits to future generations are known as adaptations. For example, a... | Biodiversity and natural selection.mp3 |
This in turn not only increases their individual chances for survival, but it also makes available more energy to the taller redwoods to produce more seeds that carry this tallness trait into future generations. So you get natural selection for a tallness trait and an adaptation to an environment that can present chang... | Biodiversity and natural selection.mp3 |
We have to consider, for example, that taller trees might have more trouble getting moisture from the roots all the way up to the tips of those highest branches, or that they could be more exposed to storms that could knock them down, or maybe there's some other physiological cause that we might not even have thought o... | Biodiversity and natural selection.mp3 |
Life is never simple. To me, all these aspects come together to represent the great beauties of life, this constant interplay of processes that results in the complexity of biodiversity, what Darwin called grandeur in this view of life. The flip side of this selection coin is that individuals in a population can also b... | Biodiversity and natural selection.mp3 |
You might have noticed by now that there's an important element to this story of variation, selection, and adaptation that's missing here. Darwin noticed it too, he was a very smart guy and he fully recognized that there had to be some way by which organisms could pass on those selected traits, those adaptations to the... | Biodiversity and natural selection.mp3 |
There had to be a way that the offspring of individuals that had been selected for could inherit the traits of their successful parents and ancestors. In Darwin's day, there wasn't a good understanding of a mechanism for that. It was only much later that scientists discovered how information is stored in genetic materi... | Biodiversity and natural selection.mp3 |
Today, our detailed understanding of evolutionary processes is built on the discoveries of both Darwin and geneticists. Stepping back now to put it all together, we can see that for all this to work, several different things have to be going on. You have to have variation in nature among the members of a population. Yo... | Biodiversity and natural selection.mp3 |
As we mentioned already, a germ cell is a cell that it can either go through mitosis to produce other germ cells, or it can undergo meiosis in order to produce gametes. So this is a germ cell right over here. Let me draw the nuclear membrane. So that's the nucleus. Let me draw the nucleus a little bit larger just becau... | Chromosomal crossover in Meiosis I.mp3 |
So that's the nucleus. Let me draw the nucleus a little bit larger just because that's where we care a lot about the chromosomes in it. And let me draw a centrosome, which will play a role later on. I want to do that in this blue color. Each centrosome has two centrioles in it. I just want to clarify some of the termin... | Chromosomal crossover in Meiosis I.mp3 |
I want to do that in this blue color. Each centrosome has two centrioles in it. I just want to clarify some of the terminology. And in the mitosis videos, I focused on cells of an organism, I just kind of made it up, that had two chromosomes, that had a diploid number of two, that had one homologous pair, that had one ... | Chromosomal crossover in Meiosis I.mp3 |
And in the mitosis videos, I focused on cells of an organism, I just kind of made it up, that had two chromosomes, that had a diploid number of two, that had one homologous pair, that had one chromosome from each of its parents. For this video, I'm going to focus on a species, not human beings that would have 23 pairs ... | Chromosomal crossover in Meiosis I.mp3 |
And so let's say it has two chromosomes from the father. Let me do that. I'll do that in this orange color. I'll do it in the chromatin, or I'll kind of depict the chromatin state. It's kind of unwound, so maybe it has a long one from the father, and it has a short one from the father. And then it has homologous chromo... | Chromosomal crossover in Meiosis I.mp3 |
I'll do it in the chromatin, or I'll kind of depict the chromatin state. It's kind of unwound, so maybe it has a long one from the father, and it has a short one from the father. And then it has homologous chromosomes from the mother. So it would have the long one from the mother, and it would have the short one, the s... | Chromosomal crossover in Meiosis I.mp3 |
So it would have the long one from the mother, and it would have the short one, the short one from the mother, just like that. And obviously this is a huge simplification, but hopefully this gets the point across. So here it has a diploid number of chromosomes. So this is, let me write this down, this is diploid number... | Chromosomal crossover in Meiosis I.mp3 |
So this is, let me write this down, this is diploid number is equal to, we have four chromosomes. And then this thing, this germ cell, let me write this down, this is a germ cell right over here. It will go through interphase, so let me draw that. So it will go through interphase, in which it grows, and it can replicat... | Chromosomal crossover in Meiosis I.mp3 |
So it will go through interphase, in which it grows, and it can replicate its DNA and its centrosome. And so let me draw that. So after it goes through interphase, I want to use my space carefully because I have a lot of steps to go through. After it goes through interphase, I am going to have in my nucleus, in my nucl... | Chromosomal crossover in Meiosis I.mp3 |
After it goes through interphase, I am going to have in my nucleus, in my nucleus here, my DNA will have replicated. So this long chromosome from my father, now all the DNA will have replicated. So it might look something like that. And it's attached at a centromere, all these centro words, at a centromere right here. ... | Chromosomal crossover in Meiosis I.mp3 |
And it's attached at a centromere, all these centro words, at a centromere right here. But I'm still trying to draw it in kind of the chromatin state. It's actually all spread out. It's not bunched up so you can see it very clearly as these Xs in a simple microscope. So it's just replicated. And after replicating, it i... | Chromosomal crossover in Meiosis I.mp3 |
It's not bunched up so you can see it very clearly as these Xs in a simple microscope. So it's just replicated. And after replicating, it is still one chromosome. It has twice the genetic material, but it is still one chromosome. That one chromosome is now made up of two sister chromatids. We talk a lot about that in t... | Chromosomal crossover in Meiosis I.mp3 |
It has twice the genetic material, but it is still one chromosome. That one chromosome is now made up of two sister chromatids. We talk a lot about that in the mitosis video, but it doesn't hurt to reinforce because it can get a little bit confusing. And then you have that shorter chromosome from the father. And then t... | Chromosomal crossover in Meiosis I.mp3 |
And then you have that shorter chromosome from the father. And then that also replicates into two sister chromatids attached at a centromere. So these are still two chromosomes from the father. It has twice the amount of DNA, but it's containing the same information, just duplicate versions of that same information. An... | Chromosomal crossover in Meiosis I.mp3 |
It has twice the amount of DNA, but it's containing the same information, just duplicate versions of that same information. And the same thing's going to happen from the mother. You had that long chromosome from the mother homologous to this one right over here. It's going to replicate. So it's now going to be two sist... | Chromosomal crossover in Meiosis I.mp3 |
It's going to replicate. So it's now going to be two sister chromatids. And then you have a short strand from the mother that was homologous to this one from your father. And that's also going to replicate. And so it's like that. And at the end of interphase, it would actually all be spread out. Once again, it won't be... | Chromosomal crossover in Meiosis I.mp3 |
And that's also going to replicate. And so it's like that. And at the end of interphase, it would actually all be spread out. Once again, it won't be bunched up into these clearly discernible Xs. I drew them a little bit that way, otherwise you would have trouble seeing how it replicated. And we also have replicated ou... | Chromosomal crossover in Meiosis I.mp3 |
Once again, it won't be bunched up into these clearly discernible Xs. I drew them a little bit that way, otherwise you would have trouble seeing how it replicated. And we also have replicated our centrosome as we've gone through interphase. Now we are ready. In fact, now we are ready for either mitosis or meiosis. But ... | Chromosomal crossover in Meiosis I.mp3 |
Now we are ready. In fact, now we are ready for either mitosis or meiosis. But as I said, the focus of this video is going to be meiosis. So let's do some meiosis. So the first several phases we call meiosis I. And the beginning of meiosis I is prophase I. So let's see what happens in prophase I. | Chromosomal crossover in Meiosis I.mp3 |
So let's do some meiosis. So the first several phases we call meiosis I. And the beginning of meiosis I is prophase I. So let's see what happens in prophase I. So prophase I, so let me draw the cell right over here. So prophase I, a couple of things happen. The nuclear membrane begins to dissolve. | Chromosomal crossover in Meiosis I.mp3 |
So let's see what happens in prophase I. So prophase I, so let me draw the cell right over here. So prophase I, a couple of things happen. The nuclear membrane begins to dissolve. This is very similar to prophase when we were looking at mitosis. So the nuclear envelope begins to dissolve. These things start to maybe mi... | Chromosomal crossover in Meiosis I.mp3 |
The nuclear membrane begins to dissolve. This is very similar to prophase when we were looking at mitosis. So the nuclear envelope begins to dissolve. These things start to maybe migrate a little bit. So these characters are starting to go at different ends. And the DNA starts to bunch up into kind of its condensed for... | Chromosomal crossover in Meiosis I.mp3 |
These things start to maybe migrate a little bit. So these characters are starting to go at different ends. And the DNA starts to bunch up into kind of its condensed form. So now I can start to draw it as proper. So this is the one from the father right over here. And this is the one from the mother. And I'm drawing th... | Chromosomal crossover in Meiosis I.mp3 |
So now I can start to draw it as proper. So this is the one from the father right over here. And this is the one from the mother. And I'm drawing them overlapping on purpose because something very interesting happens, especially in meiosis. So this is the mother right over here. This is, let me see, I'll do the centrom... | Chromosomal crossover in Meiosis I.mp3 |
And I'm drawing them overlapping on purpose because something very interesting happens, especially in meiosis. So this is the mother right over here. This is, let me see, I'll do the centromere in blue now. That's a centromere. That's the centromere. Now this is the shorter ones from the father. These are the shorter o... | Chromosomal crossover in Meiosis I.mp3 |
That's a centromere. That's the centromere. Now this is the shorter ones from the father. These are the shorter ones from the mother. And actually let me just draw them on opposite sides just to show that they don't have to, the ones from the father aren't always on the left-hand side. So this is the shorter one from t... | Chromosomal crossover in Meiosis I.mp3 |
These are the shorter ones from the mother. And actually let me just draw them on opposite sides just to show that they don't have to, the ones from the father aren't always on the left-hand side. So this is the shorter one from the father. They could be all on the left-hand side, but it doesn't necessarily have to be.... | Chromosomal crossover in Meiosis I.mp3 |
They could be all on the left-hand side, but it doesn't necessarily have to be. And then this is the shorter one from the mother. And I won't draw these overlapping, although they could have. Shorter one from the mother. And once again, each of these, this is a homologous pair. That's a homologous pair over there. Now ... | Chromosomal crossover in Meiosis I.mp3 |
Shorter one from the mother. And once again, each of these, this is a homologous pair. That's a homologous pair over there. Now the DNA has been replicated, so in each of the chromosomes in a homologous pair, you have two sister chromatids. And so in this entire homologous pair, you have four chromatids. And so this is... | Chromosomal crossover in Meiosis I.mp3 |
Now the DNA has been replicated, so in each of the chromosomes in a homologous pair, you have two sister chromatids. And so in this entire homologous pair, you have four chromatids. And so this is sometimes called a tetrad. So let me just give ourselves some terminology. So this right over here is called a tetrad, or o... | Chromosomal crossover in Meiosis I.mp3 |
So let me just give ourselves some terminology. So this right over here is called a tetrad, or often called a tetrad. Now the reason why I drew this overlapping is when we are in prophase one, in meiosis one, let me label this, this is prophase one, you can get some genetic recombination, some homologous recombination.... | Chromosomal crossover in Meiosis I.mp3 |
Once again, this is a homologous pair, one chromosome from the father, that I've gotten from the father, the species or the cell got from its father cell, and one from the mother. And they're homologous in that they might contain different base pairs, different actual DNA, but they code for the same genes. So, you know... | Chromosomal crossover in Meiosis I.mp3 |
And the reason why I overlapped them like this is to show how the recombination can occur. So actually, let me zoom in. So this is the one from the father, once again, it's in all in the condensed form. This is one chromosome made up of two sister chromatids right over here, and I drew the centromere, not to be confuse... | Chromosomal crossover in Meiosis I.mp3 |
This is one chromosome made up of two sister chromatids right over here, and I drew the centromere, not to be confused with centrosomes, that's where they are, those two sister chromatids are attached. And then I will draw the homologous chromosome from the mother. So the homologous chromosome from the mother, just lik... | Chromosomal crossover in Meiosis I.mp3 |
And the recombination can occur at a point right over here. So after you're done the recombination, this side might look something more like this. So let me draw it like this. So they essentially break up and swap those little sections, is one way to think about it. So this one will now have a little piece from the mot... | Chromosomal crossover in Meiosis I.mp3 |
So they essentially break up and swap those little sections, is one way to think about it. So this one will now have a little piece from the mother, and it might code for similar genes, but now it contains the mother's genetic information. And then this one over here will now have the piece, and you could say even the ... | Chromosomal crossover in Meiosis I.mp3 |
Let me do this to two centromeres. And this is really interesting. All the time there could be recombination, and often times it can lead to non-optimal things, nonsense code in DNA, and might lead to a non-functional organism. But this happens fairly common in meiosis. And it's a way, once again, to get more variation... | Chromosomal crossover in Meiosis I.mp3 |
But this happens fairly common in meiosis. And it's a way, once again, to get more variation. We've talked about sexual reproduction before, and sexual reproduction introduces variation into a population. And this, obviously, when different sperms find different eggs, that introduces variation. But then even amongst ho... | Chromosomal crossover in Meiosis I.mp3 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.