Sentence stringlengths 132 1.56k | video_title stringlengths 11 103 |
|---|---|
So there's a homologous pair. This is one chromosome right here. That's another chromosome right there. On this chromosome in the homologous pair, there might be, at the eye color locus, there's the brown eye gene. And at this one, at the eye color locus, there's a blue eye gene. And similarly for my dad, when you look... | Introduction to Heredity.mp3 |
On this chromosome in the homologous pair, there might be, at the eye color locus, there's the brown eye gene. And at this one, at the eye color locus, there's a blue eye gene. And similarly for my dad, when you look at that same chromosome in his cells, let me do them like this. So this is one chromosome there, and th... | Introduction to Heredity.mp3 |
So this is one chromosome there, and this is the other chromosome here. When you look at that locus on this chromosome or that location, it has the brown-eyed allele for that gene, and on this one, it has the blue-eyed allele on this gene. And we learn from meiosis when the chromosomes, well, they replicate first, and ... | Introduction to Heredity.mp3 |
And we don't know which way they line up. For example, my dad might give me this chromosome or might give me that chromosome, or my mom might give me that chromosome or might give me that chromosome. So I could have any of these combinations. So for example, if I get this chromosome from my mom and this chromosome from... | Introduction to Heredity.mp3 |
So for example, if I get this chromosome from my mom and this chromosome from my dad, what is the genotype going to be for eye color? Well, it's going to be capital B and capital B. If I get this chromosome from my mom and this chromosome from my dad, what's it going to be? Well, I'm going to get the big B from my dad,... | Introduction to Heredity.mp3 |
Well, I'm going to get the big B from my dad, and then I'm going to get the lowercase b from my mom. So this is another possibility. Now, this is another possibility here where I get the brown-eyed allele from my mom, and I get the blue-eyed allele from my dad. And then there is a possibility that I get this chromosome... | Introduction to Heredity.mp3 |
And then there is a possibility that I get this chromosome from my dad and this chromosome from my mom. So it's this situation. Now, what are the phenotypes going to be? Well, we've already seen that this one right here is going to be brown, that one's going to be brown, this one's going to be brown, but this one is go... | Introduction to Heredity.mp3 |
Well, we've already seen that this one right here is going to be brown, that one's going to be brown, this one's going to be brown, but this one is going to be blue. I already showed you this. But if I were to tell you ahead of time that, look, I have two people, they're both hybrids or they're both heterozygotes for e... | Introduction to Heredity.mp3 |
What's the probability? Well, each of these scenarios are equally likely. There's four equal scenarios. So let's put that in the denominator. Four equal scenarios. And how many of those scenarios end up with brown eyes? Well, it's 1, 2, 3. | Introduction to Heredity.mp3 |
So let's put that in the denominator. Four equal scenarios. And how many of those scenarios end up with brown eyes? Well, it's 1, 2, 3. So the probability is 3 4ths, or it's a 75% probability. Same logic. What's the probability that these parents produce an offspring with blue eyes? | Introduction to Heredity.mp3 |
Well, it's 1, 2, 3. So the probability is 3 4ths, or it's a 75% probability. Same logic. What's the probability that these parents produce an offspring with blue eyes? Well, that's only one of the four equally likely possibilities. So blue eyes is only 25%. Now, what is the probability that they produce a heterozygote? | Introduction to Heredity.mp3 |
What's the probability that these parents produce an offspring with blue eyes? Well, that's only one of the four equally likely possibilities. So blue eyes is only 25%. Now, what is the probability that they produce a heterozygote? So what is the probability that they produce a heterozygous offspring? So now we're not ... | Introduction to Heredity.mp3 |
Now, what is the probability that they produce a heterozygote? So what is the probability that they produce a heterozygous offspring? So now we're not looking at the phenotype anymore. We're looking at the genotype. So of these combinations, which are heterozygous? Well, this one is, because it's a hybrid. It has a mix... | Introduction to Heredity.mp3 |
We're looking at the genotype. So of these combinations, which are heterozygous? Well, this one is, because it's a hybrid. It has a mix of the two alleles. And so is this one. So what's the probability? Well, there's four different combinations. | Introduction to Heredity.mp3 |
It has a mix of the two alleles. And so is this one. So what's the probability? Well, there's four different combinations. All of those are equally likely, and two of them result in a heterozygote. So it's 2 4ths, or 1 half, or 50%. So using this Punnett square, and of course we had to make a lot of assumptions about t... | Introduction to Heredity.mp3 |
Well, there's four different combinations. All of those are equally likely, and two of them result in a heterozygote. So it's 2 4ths, or 1 half, or 50%. So using this Punnett square, and of course we had to make a lot of assumptions about the genes and whether one's dominant or one's recessive, we can start to make pre... | Introduction to Heredity.mp3 |
PCR was kind of the mainstay of my graduate project, where I built all sorts of different recombinant DNA molecules, and used them to learn things about plants. And so what does PCR in particular do? PCR basically makes you a lot of copies of a particular fragment of DNA that you're interested in. And so how does that,... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
And so how does that, like why would you need to make a lot of copies of a particular fragment of DNA? So you might want to be making lots of copies so that you can clone it into a plasmid, and then do some other experiments with it. That's a big use. So when we talked about cloning, and we're talking about sticking a ... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
So when we talked about cloning, and we're talking about sticking a fragment of DNA inside of a plasmid, it's not like you're just sticking one fragment into one plasmid. You're doing that with many, so you need a lot of fragments of DNA. Exactly, that is exactly it. And you might start with a very small sample of DNA.... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
And you might start with a very small sample of DNA. And so you just really need to, where else would you have to do PCR? PCR is used a lot in forensics. It's also used a lot in medical diagnostics. So this could actually be your DNA that was being checked to see if you have a gene that would predispose you to a partic... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
It's also used a lot in medical diagnostics. So this could actually be your DNA that was being checked to see if you have a gene that would predispose you to a particular condition. All sorts of really practical applications. Because it's hard to identify just one, one fragment of that gene. So you'd want to make copie... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
Because it's hard to identify just one, one fragment of that gene. So you'd want to make copies, or as they say, amplify it, so that you could run it in gels and stuff and see how all of those molecules, how big they are or something like that. Exactly, if you were just looking in your DNA pulled out of your cell, that... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
So this is how you can really zoom in and look at just the thing you need to see. Okay, so you've drawn some diagrams here, and I actually have never done a PCR, but you have, so I'm going to tell you how I understand it happening, and then you tell me if this makes sense. So what you drew over here, this is double-str... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
And let's say we want to replicate or make many, many copies of a fragment of this. And so let's say the fragment that we really care about is the fragment roughly from there to there, this part, is what we want to make, we want to make multiple copies of. And so this first step, denaturation, I have trouble pronouncin... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
It's a weird word. It's a weird word. You have 96 degrees Celsius, so this is almost at the boiling point, so it's quite hot, and that separates the two strands. Precisely. And so once they're separated, then you can cool things down, although this still isn't that cool, 55 degrees Celsius would be very uncomfortable. ... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
Precisely. And so once they're separated, then you can cool things down, although this still isn't that cool, 55 degrees Celsius would be very uncomfortable. But you would cool it down to this, and then these primers show up. And so one thing to remind ourselves is this process is happening inside of a test tube or in ... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
And so one thing to remind ourselves is this process is happening inside of a test tube or in a big solution. So you heat it up, the DNA, the two strands separate, and do you just have this primer lying around? So the primer is something that you've ordered from a company and you've ordered a lot of it. So you put in a... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
So you put in a ton of primer in your reaction so that there's a really good chance that when you get to this step here called annealing, that a primer is going to bind to many of your pieces of DNA. So this is our solution. Is this all happening in water? Water with some salts and stuff floating around, yeah. Okay, so... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
Water with some salts and stuff floating around, yeah. Okay, so we have our solution right over here. You'd put whatever your initial DNA sample is in there, and once again, it's a very small amount. You'd put a lot of that primer, so you'd want to put that in a lot of surplus. Let me do that in this magenta color. You... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
You'd put a lot of that primer, so you'd want to put that in a lot of surplus. Let me do that in this magenta color. You obviously wouldn't see it in real life. It would just all dissolve. It would just look like a drop of liquid. It would look like, but for visualization, you put a lot of primer, and so you heat it up... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
It would just all dissolve. It would just look like a drop of liquid. It would look like, but for visualization, you put a lot of primer, and so you heat it up, the DNA strands separate, and then when you cool it back down, this primer's going to be specific to the ends of the region that you want to copy. Exactly. And... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
Exactly. And so when you order online or wherever that you want a certain primer, you're going to pick the sequence of that primer to be specific to the regions you want to copy. Exactly, that's super important. Okay, and so when you cool it back down, the primer attaches, and then you heat it back up, not quite to the... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
Okay, and so when you cool it back down, the primer attaches, and then you heat it back up, not quite to the 96 degrees Celsius, but to the 72 degrees Celsius, where you extend those, and I'm assuming since it's called polymerase chain reaction, that this is where the polymerase is involved. That is exactly where the p... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
Could I just take the polymerase from my cells and throw it in there? So you actually need a special polymerase because you need one that is going to be pretty heat resistant. So as you were mentioning, even the cool step of this process is not something that your body would want to be hanging out in. So the polymerase... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
So the polymerase is actually from a really heat-tolerant microorganism. And what is that? It's called a TAC polymerase? Thermophilus aquaticus, I think? Makes quite a mouthful. And they found it at heated vents, this organism that is able to stand these high temperatures. But that, I guess, leads to another question. | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
Thermophilus aquaticus, I think? Makes quite a mouthful. And they found it at heated vents, this organism that is able to stand these high temperatures. But that, I guess, leads to another question. Why do you have to heat it up to begin with? I guess just to separate the two strands? That's really the key reason. | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
But that, I guess, leads to another question. Why do you have to heat it up to begin with? I guess just to separate the two strands? That's really the key reason. You just have to get them apart. You don't have an enzyme to do it the way you might in a cell, so heat does the trick. Okay, so I get it. | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
That's really the key reason. You just have to get them apart. You don't have an enzyme to do it the way you might in a cell, so heat does the trick. Okay, so I get it. So this is one step. I'm guessing I'm getting at least the polymerase part of the PCR, where you heat it up, the strands separate, then you have all of... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
Okay, so I get it. So this is one step. I'm guessing I'm getting at least the polymerase part of the PCR, where you heat it up, the strands separate, then you have all of this extra primer there. The primer, because there's so much primer, the primer's much more likely to bind to at least at this part of the sequence t... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
The primer, because there's so much primer, the primer's much more likely to bind to at least at this part of the sequence than for these two strands to get back together at this point. And then you have the polymerase, the TAC polymerase in particular. And you would have added that at the beginning, you know, the TAC ... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
I guess I'll put it in this, I'll do it in a yellow color. So you would also put all that TAC polymerase in there. And once again, these things aren't robots. They don't know exactly what they need to do. They just bump into things in the right way and react in the right way. And then you would also have to add a bunch... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
They don't know exactly what they need to do. They just bump into things in the right way and react in the right way. And then you would also have to add a bunch of nucleotides. Yes, absolutely. Your reaction is not going to work if you forget the nucleotides. So the TAC polymerase, when you heat it back up again after... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
Yes, absolutely. Your reaction is not going to work if you forget the nucleotides. So the TAC polymerase, when you heat it back up again after the primers have been attached, is going to start adding all of these nucleotides. And what, do you just wait a certain amount of time or will it just keep going on forever? It'... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
And what, do you just wait a certain amount of time or will it just keep going on forever? It'll keep going on for a while. Usually you do pick the length of that step to match how much time you expect the polymerase to need to complete your fragment. But it kind of will stop, either it'll fall off or it'll stop when y... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
But it kind of will stop, either it'll fall off or it'll stop when you go on to the next step. Okay, so this, I get this is so far. So, so far we have, after one cycle, let me, what you've written here, after one cycle we would have doubled at least that part, that part of the sequence that we care about. Although we m... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
Although we might even have, we might have copied even beyond that sequence. So where does the chain reaction come into this? So I guess you can interpret chain reaction in two ways. And one is, that's sort of what the polymerase does, is it, you know, adds things to make a chain. But there's actually even more of a ch... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
And one is, that's sort of what the polymerase does, is it, you know, adds things to make a chain. But there's actually even more of a chain reaction dimension here. And that's that we're actually getting this kind of exponential process going on. So you do it one cycle, you get to this situation right here. You heat i... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
So you do it one cycle, you get to this situation right here. You heat it up, the strands separate, you cool it down, the primers attach, you heat it up again, the Taq polymerase does its job. And like all polymerase, it goes from the five prime to the three prime direction. We talked about in that in the application. ... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
We talked about in that in the application. So now you have two strands. But now, since all of that stuff is in that solution, you can just keep, you can heat it up again. Now each of, now these two strands can turn into, or these two, these two double strands can now turn into four single strands. Then you can cool it... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
Now each of, now these two strands can turn into, or these two, these two double strands can now turn into four single strands. Then you can cool it down again. Now they get primers attached to them. And they're still the same primer because we still care about the same sequence. And then that can keep, and so now you ... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
And they're still the same primer because we still care about the same sequence. And then that can keep, and so now you go from one to two to four. And so you keep repeating this. And so how many times would it be typical for you to repeat this cycle? So like 35 might be a pretty typical number of cycles to do. It depe... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
And so how many times would it be typical for you to repeat this cycle? So like 35 might be a pretty typical number of cycles to do. It depends a little what you're doing. But you're gonna do it a lot of times. And so if you do this 35 times, I mean each time you're multiplying by two. So it's gonna be two to the 35th ... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
But you're gonna do it a lot of times. And so if you do this 35 times, I mean each time you're multiplying by two. So it's gonna be two to the 35th power, which is well over a billion times. So, and how long would that take? You've done this before. Um, depends on the length of your fragment, but usually like two to th... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
So, and how long would that take? You've done this before. Um, depends on the length of your fragment, but usually like two to three hours. So in two to three hours, you can start with one fragment and get into the billions. If it's perfectly efficient, which I wish it always were, but you usually get quite a few piece... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
So in two to three hours, you can start with one fragment and get into the billions. If it's perfectly efficient, which I wish it always were, but you usually get quite a few pieces made. And one thing that I was, that I've always wondered when I first learned about this, and I'd like to go into a lab and do this with ... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
But I was like, well, it's, you know, it's going to be, how does it know where to stop? And you explained, well, on that first pass, it might not know where to stop. But then when you start going in the other direction, it's going to, so over here, and when it goes in the other direction, it's gonna hit a, it's going t... | Polymerase chain reaction (PCR) Biomolecules MCAT Khan Academy.mp3 |
If you look at any type of packaging on food, you'll oftentimes see a label that has protein listed in a certain number of grams per serving. And some of you who might be athletically inclined might associate it with things that help you build muscle. And none of that is incorrect. But as we'll see in this video and in... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
But as we'll see in this video and in many future videos, proteins are involved in almost every single biological process in every single living organism. And if we ask ourselves, what are they? Well, they're biomolecules. They're molecules found in biological systems. And they're large biomolecules. We could call them... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
They're molecules found in biological systems. And they're large biomolecules. We could call them macromolecules, molecules, which is just referring to, they're made up of many, many, many, many, many atoms. These right here are pictures, two different views of the chaperonin protein. And this is, the chaperonin protei... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
These right here are pictures, two different views of the chaperonin protein. And this is, the chaperonin protein is roughly 800,000 times the mass of a hydrogen atom. So it's going to contain tens of thousands of atoms, which would very much make it a macromolecule. Now, one thing to be careful of, even though these a... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
Now, one thing to be careful of, even though these are very, very large on a molecular scale, even the largest protein we know of, titin, is about one micrometer in length. And that's much larger than this chaperonin here. And a micrometer is 1,000th of a millimeter. So even the largest proteins are microscopic. Now, a... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
So even the largest proteins are microscopic. Now, another way to think about proteins is what they are made up of. So some proteins are made up of a single chain of something called amino acids. And things like chaperonin are made up of multiple chains of amino acids. So in a little bit, I'll show you some particular ... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
And things like chaperonin are made up of multiple chains of amino acids. So in a little bit, I'll show you some particular amino acids. But for now, just think of them as the building blocks of proteins. So let's say that's an amino acid, and then it will bond to another amino acid. And it's not just one type of amino... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
So let's say that's an amino acid, and then it will bond to another amino acid. And it's not just one type of amino acid. And they can form these really, really, really long chains. And so let me be very clear. This is an amino acid. And it's called that because it contains an amine group, which you don't have to worry... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
And so let me be very clear. This is an amino acid. And it's called that because it contains an amine group, which you don't have to worry about for now. And they are the monomers that form the polymers of what's known as polypeptide chains. So these are monomers. You connect them together, and you can keep going. You ... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
And they are the monomers that form the polymers of what's known as polypeptide chains. So these are monomers. You connect them together, and you can keep going. You can have hundreds or even thousands of these. And so this whole thing right over here, you can consider to be a polymer. And a chain of amino acids, the p... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
You can have hundreds or even thousands of these. And so this whole thing right over here, you can consider to be a polymer. And a chain of amino acids, the polymer of amino acids, is known as a polypeptide, polypeptide. And sometimes a polypeptide chain is a protein, but sometimes a protein can be made up of multiple ... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
And sometimes a polypeptide chain is a protein, but sometimes a protein can be made up of multiple polypeptide chains put together. And what happens is, after these amino acids connect or bond to each other, they bend, and they form the shape of these proteins. So you can imagine the chaperonin protein right over here.... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
It has these chains of amino acids that bend, that have a conformation that form this shape. And that's really what gives proteins their power. And as I mentioned, proteins are involved in almost every single biological function. They play a structural, structural role. They play a mechanical role. When your muscles co... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
They play a structural, structural role. They play a mechanical role. When your muscles contract, you have actin and myosin proteins interacting with each other so that your muscle contracts. They can act as enzymes, which we will talk about in a lot more depth in future videos. Enzymes help catalyze reactions. They he... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
They can act as enzymes, which we will talk about in a lot more depth in future videos. Enzymes help catalyze reactions. They help biological, biochemical reactions happen in biological systems. They can be involved with the immune system. They could be involved with signaling. They can send signals from one part of th... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
They can be involved with the immune system. They could be involved with signaling. They can send signals from one part of the body to another, or they can be receptors on cells that receive signals. So proteins are incredibly, incredibly important. Now, with that out of the way, let's dig a little bit deeper into the ... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
So proteins are incredibly, incredibly important. Now, with that out of the way, let's dig a little bit deeper into the building blocks of proteins, the monomers that build up the polymers that are polypeptides, which could be proteins or which could be used to build up proteins. So what we see on the left here is the ... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
Notice you see some oxygens, you see some hydrogens, some carbons, and a nitrogen. And then bonded to this carbon right over here, you see this R, and you say, what element is that? Well, this is not an element. This is referring, this is kind of a placeholder for a side chain, which differentiates the common amino aci... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
This is referring, this is kind of a placeholder for a side chain, which differentiates the common amino acids. And you see some of the common amino acids in this diagram right over here. And you can see what the R would be. For this arginine right over here, that R group would be this part. And you don't have to under... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
For this arginine right over here, that R group would be this part. And you don't have to understand the biochemistry of it in too much detail, but you can see that they all have this top part in common, but then they all have a different R group. Right over here. And it's different sequences of these amino acids that ... | https%3A%2F%2Fcdn.kastatic.org%2Fka-youtube-converted%2F78QUeXVKiJ4.mp4%2F78QUeXVKiJ4.mp4%23t%3D0.mp3 |
Next up, biogeography. Well, biogeography is the study of how animals, plants, and other organisms have come to occupy the places on the globe that they do. Imagine a new island being born in the middle of the ocean. At first, it's a hunk of rock, lifeless. But gradually, seeds and insects and small animals originating... | Biogeography Where Life Lives.mp3 |
At first, it's a hunk of rock, lifeless. But gradually, seeds and insects and small animals originating from nearby landmasses get blown over on the winds. They come crashing ashore, pushed by the waves. Not all the organisms make it. But those that do, with time, adapt to island living, perhaps even evolving into new ... | Biogeography Where Life Lives.mp3 |
Not all the organisms make it. But those that do, with time, adapt to island living, perhaps even evolving into new species. Just take birds. There are the finches of the Galapagos Islands, the birds of paradise of Papua New Guinea, the honeycreepers of Hawaii, and so on. In each case, a single island species diversifi... | Biogeography Where Life Lives.mp3 |
There are the finches of the Galapagos Islands, the birds of paradise of Papua New Guinea, the honeycreepers of Hawaii, and so on. In each case, a single island species diversified into an array of species found nowhere else on Earth. Species also got something to say about why some closely related species flourish on ... | Biogeography Where Life Lives.mp3 |
It seems odd, until you recall that Earth didn't always look this way. A few hundred million years ago, all land was part of Pangaea, a hulking supercontinent. There were no vast oceans to interfere with the movements of organisms. But then, starting about 170 million years ago, the continent drifted like vast rafts ac... | Biogeography Where Life Lives.mp3 |
If it's colored in, that means that they exhibit the trait. In this case, it's colorblindness. So Bill exhibits colorblindness. His phenotype is colorblind, while Bonnie does not exhibit colorblindness. Colorblindness is an X-linked recessive trait. If Barbara is expecting another child, so this is Barbara right here, ... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
His phenotype is colorblind, while Bonnie does not exhibit colorblindness. Colorblindness is an X-linked recessive trait. If Barbara is expecting another child, so this is Barbara right here, what is the probability that it will be colorblind? So pause this video and see if you can figure that out on your own. All righ... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
So pause this video and see if you can figure that out on your own. All right, now let's work through this together. So they're asking us about their next child here. What is the probability that it is going to be colorblind? And to help us with that, we can try to figure out the genotypes of Tom and Barbara. So Tom is... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
What is the probability that it is going to be colorblind? And to help us with that, we can try to figure out the genotypes of Tom and Barbara. So Tom is pretty straightforward. He is male, we know that because there's a square there. So X, he has an X chromosome and he has a Y chromosome. And colorblindness is an X-li... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
He is male, we know that because there's a square there. So X, he has an X chromosome and he has a Y chromosome. And colorblindness is an X-linked recessive trait. And so let me just make clear what's going on. So I'll do lowercase c for colorblind, colorblind. And I could do a capital C for the dominant trait, which i... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
And so let me just make clear what's going on. So I'll do lowercase c for colorblind, colorblind. And I could do a capital C for the dominant trait, which is not colorblind. But since they look so similar, I'll just use a plus for not colorblind, not colorblind. And so Tom, his phenotype, he is colorblind. And he only ... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
But since they look so similar, I'll just use a plus for not colorblind, not colorblind. And so Tom, his phenotype, he is colorblind. And he only has one X chromosome where the colorblind, what the colorblind trait is linked to. And so that must have the recessive allele right over there. So this is Tom's genotype. But... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
And so that must have the recessive allele right over there. So this is Tom's genotype. But what about Barbara? Well, we know Barbara's going to have two X chromosomes because Barbara is female. And we know that both of them can't be lowercase c because then Barbara would exhibit colorblindness. But how can we figure o... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
Well, we know Barbara's going to have two X chromosomes because Barbara is female. And we know that both of them can't be lowercase c because then Barbara would exhibit colorblindness. But how can we figure out her actual genotype? Well, we could look at her parents. So Bill over here is going to have the same genotype... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
Well, we could look at her parents. So Bill over here is going to have the same genotype as Tom, at least with respect to colorblindness. He is male, so he has an X chromosome and a Y chromosome. And because he exhibits colorblindness, that X chromosome must have the recessive colorblind allele associated with it. Now ... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
And because he exhibits colorblindness, that X chromosome must have the recessive colorblind allele associated with it. Now Bonnie, we do not know. She will be XX, will have two X chromosomes. Like Barbara, we know that both of these can't have the recessive allele because then Bonnie would be filled in. She would exhi... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
Like Barbara, we know that both of these can't have the recessive allele because then Bonnie would be filled in. She would exhibit colorblindness. But we don't know whether she is a carrier or whether she isn't. But let's just think about where Barbara got her chromosomes from. One of her X chromosomes comes from her f... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
But let's just think about where Barbara got her chromosomes from. One of her X chromosomes comes from her father. And the other one comes from her mother. So if she got this X chromosome from her father, her father only has one X chromosome to give, the one that has the colorblind allele. So if this is from her father... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
So if she got this X chromosome from her father, her father only has one X chromosome to give, the one that has the colorblind allele. So if this is from her father, it must have the colorblind allele here. And we know that the one from her mother does not have the colorblind allele because if it was like this, then Ba... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
So we know that this must be a plus here. It is the dominant non-colorblind allele. And so now we know both of their genotypes. And we can use those to then figure out the possible outcomes for their offspring. So for example, Tom can contribute a X chromosome that has a colorblind allele or a Y chromosome. And Barbara... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
And we can use those to then figure out the possible outcomes for their offspring. So for example, Tom can contribute a X chromosome that has a colorblind allele or a Y chromosome. And Barbara, right over here, can contribute an X chromosome that has a colorblind allele or an X chromosome that has the non-colorblind al... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
Barbara is a carrier. And so let me just draw a little Punnett square here. And so we have four possible outcomes for their children, and they're all equally likely. So you can get the X chromosome from Barbara that has a colorblind allele and the X chromosome from Tom that has the colorblind allele. You could have the... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
So you can get the X chromosome from Barbara that has a colorblind allele and the X chromosome from Tom that has the colorblind allele. You could have the X chromosome from Barbara with the colorblind allele and the Y chromosome from Tom. You could have the non-colorblind X chromosome, or the X chromosome that does not... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
Or you could have the non-colorblind X chromosome and the Y chromosome from the father. So there's four equal scenarios. And so in how many of these scenarios is the offspring colorblind? Well, here we have a colorblind female. She has two of the recessive alleles, so that female will be colorblind. This is a female ca... | Pedigree for determining probability of exhibiting sex linked recessive trait Khan Academy.mp3 |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.