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But what if you could insert into the DNA of that apple tree maybe a gene that makes it more resistant to that disease? And this is what people actually do today. So they will insert, insert DNA, and it could be some pretty wild things. I've read stories about inserting insect DNA into a plant so that it will be more r... | Introduction to genetic engineering Molecular genetics High school biology Khan Academy.mp3 |
I've read stories about inserting insect DNA into a plant so that it will be more robust in some way or another. Now, this idea of recombinant DNA and genetically modifying food, this is often known as a genetically modified organism, this is somewhat controversial. Many people say, hey, this is good. It allows us to p... | Introduction to genetic engineering Molecular genetics High school biology Khan Academy.mp3 |
It allows us to produce more robust foods. In fact, part of this recombinant DNA, inserting DNA into something else, it might make it more nutritious. It might provide for more vitamins. But other people would argue that, hey, we don't know exactly what all the repercussions of what we're doing will happen. We might th... | Introduction to genetic engineering Molecular genetics High school biology Khan Academy.mp3 |
But other people would argue that, hey, we don't know exactly what all the repercussions of what we're doing will happen. We might think it's helpful, but when you're taking DNA from one organism and putting it into another, how does that affect the nutrition or the long-lasting effects of eating that over time? So thi... | Introduction to genetic engineering Molecular genetics High school biology Khan Academy.mp3 |
As we have more and more control over the genome, and especially as we'll see the human genome, there's questions that we have to ask about, is it good or is it bad? But going back to this idea of genetic engineering and recombinant DNA, other things that you could do is, you could, let's say that we need to produce in... | Introduction to genetic engineering Molecular genetics High school biology Khan Academy.mp3 |
And then all of a sudden, that bacteria cell can become a human insulin-producing factory so that we could have more insulin for diabetics, that this insulin could then be harvested. That is a use of recombinant DNA. And so we really are going into an interesting period in humanity. For many thousands of years, we were... | Introduction to genetic engineering Molecular genetics High school biology Khan Academy.mp3 |
For many thousands of years, we were breeding things, but now we're learning to manipulate things at a very fine-grain level. And it makes us ask all sorts of questions. There are likely to be some very good things we can do, produce new medicines, produce more robust crops, but there are also questions about what are ... | Introduction to genetic engineering Molecular genetics High school biology Khan Academy.mp3 |
Let's face it, if you take a bunch of beautiful flowers and plant them in your garden, you're increasing the biodiversity in your garden, right? You raise the species richness in your garden. But it's not a simple additive equation. It's more complicated than that. The term introduced species is synonymous with exotic ... | Introduced species and biodiversity.mp3 |
It's more complicated than that. The term introduced species is synonymous with exotic species. The definition is any species that through the activities of humans is knowingly or accidentally transferred from its native habitat into one in which it doesn't naturally occur. An introduced species is the opposite of a na... | Introduced species and biodiversity.mp3 |
An introduced species is the opposite of a native species, which is one that occurs in an area naturally, without human intervention. Many introductions are intentional. We do it on purpose, and we've been doing that for a heck of a long time, probably ever since humans came onto the scene and realized that they could ... | Introduced species and biodiversity.mp3 |
From goats and pigs to cattle and crops. Mostly we transport organisms that will do some good for us through agricultural means. We've been introducing plants and animals to places where they weren't native for a long, long time. Usually when people think about introduced species, they're really thinking more about the... | Introduced species and biodiversity.mp3 |
Usually when people think about introduced species, they're really thinking more about the accidental ones, the things that happened coincidentally alongside human activities. When we introduce a species to a new area, everything that's living on, in, or with that species comes along with it. If you pick up a cow from ... | Introduced species and biodiversity.mp3 |
I think people immediately picture images of rats streaming off the ships when they pull into some beautiful Tahitian paradise. Or the snakes that came into Guam with military movements during World War II. These animals are legendary in doing damage to native birds. They're very obvious ways that introduced organisms ... | Introduced species and biodiversity.mp3 |
They're very obvious ways that introduced organisms radically change biodiversity in a single place. There are so many other subtle ways that introductions happen and cause problems. The bottom line is that the world economy is hit with an annual cost of $1.4 trillion dealing with the negative impacts, obvious and not ... | Introduced species and biodiversity.mp3 |
That's a number I have a hard time wrapping my mind around. If you had an extra $1.4 trillion to play around with, there's a lot of possibility to do some good in the world. Because humans have been introducing new species for a long time, the concept of native habitat is a little bit slippery. The human activities tha... | Introduced species and biodiversity.mp3 |
The human activities that caused the transfer can happen long before we recognize that it actually happened. So that sometimes, the history of an introduction can be lost. When we aren't sure of the history, up until the point we are sure or have some reasonable evidence, we call those species cryptogenic. Crypto means... | Introduced species and biodiversity.mp3 |
Crypto means hidden. Genic means origin. Solving the riddles of cryptogenic species underscores another reason why collections are so important. The only way to trace the origins of introductions is to know what was there beforehand. Collections can preserve that historical information, and collections made today estab... | Introduced species and biodiversity.mp3 |
The only way to trace the origins of introductions is to know what was there beforehand. Collections can preserve that historical information, and collections made today establish baselines for future reference. If those collections are maintained in perpetuity, those baselines are going to be good 100 years from now o... | Introduced species and biodiversity.mp3 |
So we can use collections to try and get answers to this problem. Not all species are, in fact, harmful. Actually they're not all harmful to us because the ones that we introduce on purpose are ones that are there for our benefit. Some introduced species can provide new food sources or even habitats for native species.... | Introduced species and biodiversity.mp3 |
Some introduced species can provide new food sources or even habitats for native species. Native species aren't always helpless and harmed. They can make use of some of the newcomers. Introduced grasses and corn, for example, are eaten by native species, and certain trees that have been introduced can serve as habitats... | Introduced species and biodiversity.mp3 |
Introduced grasses and corn, for example, are eaten by native species, and certain trees that have been introduced can serve as habitats for birds. Some introduced species live under our radar. We don't even know they're there, doing little perceivable damage to the ecosystem by reducing species richness. But some intr... | Introduced species and biodiversity.mp3 |
But some introduced species certainly go beyond just living peacefully alongside the natives. They can do this because they have competitive advantages. They lack natural controls, such as the predators or diseases that keep them in check in their native habitats. Some invasive species are generalists, which means they... | Introduced species and biodiversity.mp3 |
Some invasive species are generalists, which means they can tolerate, reproduce rapidly, and thrive in a wide range of environmental conditions, allowing them to successfully compete with and overwhelm native populations. When introduced species take over an environment at the expense of native species, they're known a... | Introduced species and biodiversity.mp3 |
Here's an example of consequences for humans as well as for species richness. In 1992, an introduced species of comb jelly was found in the Black Sea. Comb jellies are weird, transparent, jellyfish-like forms with a voracious appetite for fish larvae and eggs. Within months, that single introduction resulted in the tot... | Introduced species and biodiversity.mp3 |
Within months, that single introduction resulted in the total collapse of the anchovy fishery in the Black Sea. Comb jellies tolerated the conditions in the Black Sea, and their population exploded at the expense of the anchovies. The bottom line here is that introduced species can outcompete the natives for food, for ... | Introduced species and biodiversity.mp3 |
They alter the ecosystem's food webs, disturbing crucial elements and interactions that would otherwise contribute to healthy ecosystem function. The comb jelly is a good example of that. Sure, your species list for the Black Sea has gone up by one, but it destroyed all the anchovies. You have to take a species off the... | Introduced species and biodiversity.mp3 |
You have to take a species off the list. Plus, perhaps whatever else was eating the anchovies. And before you know it, because there's nothing for the comb jellies to eat anymore, they're gone too. So, not only have you not added a species, but in the end you've actually subtracted a whole bunch. So invasive species ar... | Introduced species and biodiversity.mp3 |
So, not only have you not added a species, but in the end you've actually subtracted a whole bunch. So invasive species are, ultimately, organisms that cause decreases in ecosystem function. That's another definition of invasives that we need to come to grips with. What's worse, invasives very seldom come by themselves... | Introduced species and biodiversity.mp3 |
What's worse, invasives very seldom come by themselves. As I was saying with the cow example, they often come with new diseases, new parasites, new accompanying effects that we can hardly predict. Another good example of invasives are pathogens, something that we don't often consider as invasives. These include disease... | Introduced species and biodiversity.mp3 |
These include disease-causing organisms like fungi or bacteria and even viruses. These are things that we also introduce to wild populations, and there are extinctions that come from that. In fact, in the past 500 years, we've directly caused the extinction of more than 100 species of birds, partly through the introduc... | Introduced species and biodiversity.mp3 |
And heck knows what damage we did to organisms that were depending on those birds. In the forest realm, Dutch Elm Disease was something that, when I was growing up, was a huge thing, and actually it still is. In North America, Dutch Elm Disease left skeletal trees for miles and miles. When I was a kid growing up in Tor... | Introduced species and biodiversity.mp3 |
When I was a kid growing up in Toronto in the 60s, 80% of the elms in the city were killed, and it was really sad. Those trees were not only gorgeous, they were very important lumber. Elm trees were a direct service to us in so many different ways, from producing shade to furniture. The fungus was introduced by bark be... | Introduced species and biodiversity.mp3 |
The fungus was introduced by bark beetles, some of which were native and some of which were introduced, both of which supported and co-evolved with the fungal pathogen, which could not be stopped. This idea of being a generalist, the ability to reproduce and displace natives, the ability to become more abundant at the ... | Introduced species and biodiversity.mp3 |
And the first type of transport of molecule across membranes that I'm going to talk about is transport that does not require energy. It's all about molecules moving down their concentration gradient. And that type of transport we call passive transport. Passive transport. So it does not require energy. It's really just... | Passive transport and selective permeability Biology Khan Academy.mp3 |
Passive transport. So it does not require energy. It's really just about things moving down their concentration gradient. So down, let me write move down concentration gradient. Move down concentration, concentration gradient. Now, if you have this cellular membrane, a lot of things might want to move down their concen... | Passive transport and selective permeability Biology Khan Academy.mp3 |
So down, let me write move down concentration gradient. Move down concentration, concentration gradient. Now, if you have this cellular membrane, a lot of things might want to move down their concentration gradient, but this membrane is selectively permeable. It's going to be more or less permeable to different types o... | Passive transport and selective permeability Biology Khan Academy.mp3 |
It's going to be more or less permeable to different types of molecules. So let's think about these different types of molecules and think about how they might diffuse passively across the membrane. So if we have really small molecules, we can say, okay, they might be able to fit in the gaps between the hydrophilic hea... | Passive transport and selective permeability Biology Khan Academy.mp3 |
So being small is good. So small, if you're small, that aids transport, passive transport. It aids diffusion across the membrane. And in particular, it really helps to be small and non-charged. Small and no charge. So examples of that could be things like carbon dioxide. So carbon dioxide, it's a small molecule. | Passive transport and selective permeability Biology Khan Academy.mp3 |
And in particular, it really helps to be small and non-charged. Small and no charge. So examples of that could be things like carbon dioxide. So carbon dioxide, it's a small molecule. It doesn't have a charge. So carbon dioxide molecules, if I have a higher concentration on the outside, on the outside, actually let me ... | Passive transport and selective permeability Biology Khan Academy.mp3 |
So carbon dioxide, it's a small molecule. It doesn't have a charge. So carbon dioxide molecules, if I have a higher concentration on the outside, on the outside, actually let me do it the other way around. Let's say I have a higher concentration on the inside than I have on the outside. Well, just as we learned in the ... | Passive transport and selective permeability Biology Khan Academy.mp3 |
Let's say I have a higher concentration on the inside than I have on the outside. Well, just as we learned in the diffusion video, in a given amount of time, you're gonna have more carbon dioxide molecules interacting with the bottom, going from inside of the cell and interacting with the membrane than from the outside... | Passive transport and selective permeability Biology Khan Academy.mp3 |
And they're gonna have more on the inside interacting with the membrane than the outside. And so since they're small, some of them are gonna be able to pass through, and they're also not going to be bothered by the hydrophobic tails. And they're gonna have things going both ways, but you're gonna have more going from t... | Passive transport and selective permeability Biology Khan Academy.mp3 |
So they're gonna move along with their concentration gradient. So carbon dioxide can actually diffuse quite well across cellular membranes. Another molecule that can is molecular oxygen. Molecular oxygen can also diffuse quite well across cellular membranes. So if I have a higher concentration of oxygen on the outside ... | Passive transport and selective permeability Biology Khan Academy.mp3 |
Molecular oxygen can also diffuse quite well across cellular membranes. So if I have a higher concentration of oxygen on the outside than I have on the inside, because it's small and it's non-charged, it's not gonna have problems. It's not gonna be particularly attracted to the hydrophilic heads, but they're small, and... | Passive transport and selective permeability Biology Khan Academy.mp3 |
It's gonna be indifferent to them. And then it's gonna be able to pass through all these hydrophobic tails. And since you have a higher concentration on the outside than the inside, you're just going to have more in a given amount of time, more random interactions of the ones going in that direction than the ones going... | Passive transport and selective permeability Biology Khan Academy.mp3 |
So you would have a net inflow into the cells. So these things are going to be able to diffuse fairly, fairly, whoops, these things are gonna be able to diffuse fairly, fairly naturally. Now, and of course they are going to be obstructed by just the structure, by all of these molecules here that make up the actual cell... | Passive transport and selective permeability Biology Khan Academy.mp3 |
Now, what about things that would have a lot of trouble getting through? So things that would have a lot of trouble getting through would be things like a sodium ion, a sodium ion, or a potassium, or a potassium ion. Why would they have trouble getting through? Well, let's just imagine. Let's say I have a higher concen... | Passive transport and selective permeability Biology Khan Academy.mp3 |
Well, let's just imagine. Let's say I have a higher concentration of sodium on the outside, on the outside, than I have on the inside. Well, they might be attracted to the hydrophilic heads here that have some charge, but there's no reason why they would then want to go any further. They're going to be attracted to the... | Passive transport and selective permeability Biology Khan Academy.mp3 |
They're going to be attracted to the hydrophilic heads that have charge, and they're not going to, and the hydrophobic tails have nothing interesting for them. They're gonna wanna maybe clump around the phosphate heads, but not be able to migrate all the way through. So things that have outright charge are gonna have t... | Passive transport and selective permeability Biology Khan Academy.mp3 |
We'll see in future videos that there's other ways for them to get through. You have things like channel proteins, which essentially give them tunnels, and we'll talk more about that, but just naturally, natural diffusion is going to be hard for things like this. Now, what about things that are in between? What about t... | Passive transport and selective permeability Biology Khan Academy.mp3 |
What about things like water molecules? And water is incredibly important because cells are living in an aqueous environment. They're surrounded by water on the inside of the cell and the outside of the cell. And water is in between because it doesn't have an outright charge, but it has a partially water molecules, oxy... | Passive transport and selective permeability Biology Khan Academy.mp3 |
And water is in between because it doesn't have an outright charge, but it has a partially water molecules, oxygen, two hydrogens. Oxygen likes to hog the electrons, has a partial negative charge on that end. The hydrogens have their electrons charged, have a partial positive, and a partial positive charge on that end.... | Passive transport and selective permeability Biology Khan Academy.mp3 |
And we call these phosphate heads hydrophilic because they're attracted to water and water's attracted to it. So the water molecules, the water molecules for sure are going to be attracted to the hydrophilic heads, but their charge isn't so strong, it isn't so strong that they can't, if you have enough interactions, a ... | Passive transport and selective permeability Biology Khan Academy.mp3 |
It has some polarity, but it's going to be able to make it through. Not as easily as a carbon dioxide or the molecular oxygen, but it will be able to slowly diffuse through. And as we'll see, there's other ways that this can be facilitated, right, where the water can go through once again, these we'll see in future vid... | Passive transport and selective permeability Biology Khan Academy.mp3 |
Perhaps the most mind-blowing idea in all of biology is the concept that all living things we know of, based on current evidence that we have, all originated from a common ancestor. So it doesn't matter whether we're talking about a simple bacterial cell, which actually in reality isn't so simple after all, a tree made... | Cellular evidence of common ancestry Natural selection AP Biology Khan Academy (2).mp3 |
This is an example right over here. This is saying the same thing, that everything that we see in the world today, all living things, regardless of what domain they're in, and we would be a subset of animals right over here. There's so many animal species that they all share a common ancestor several billions of years ... | Cellular evidence of common ancestry Natural selection AP Biology Khan Academy (2).mp3 |
But you should be skeptical. We are scientists here. How do we believe this? What is the evidence for that? And one piece of evidence is by looking at the cellular level and look at commonalities amongst different groups and realize that it would be unlikely for them to develop independently of each other. For example,... | Cellular evidence of common ancestry Natural selection AP Biology Khan Academy (2).mp3 |
What is the evidence for that? And one piece of evidence is by looking at the cellular level and look at commonalities amongst different groups and realize that it would be unlikely for them to develop independently of each other. For example, all life forms that we know of have DNA. They all have RNA. And it isn't jus... | Cellular evidence of common ancestry Natural selection AP Biology Khan Academy (2).mp3 |
They all have RNA. And it isn't just how they encode information. It's also processes, biochemical processes, that occur in the cells. They all have some form of glycolysis. But this seems, and these aren't the only things that we've observed are common to all life forms. They're all based on cells as the basic units, ... | Cellular evidence of common ancestry Natural selection AP Biology Khan Academy (2).mp3 |
They all have some form of glycolysis. But this seems, and these aren't the only things that we've observed are common to all life forms. They're all based on cells as the basic units, which are bound by a membrane. And so in theory, these things, I guess, could have developed independently of each other without having... | Cellular evidence of common ancestry Natural selection AP Biology Khan Academy (2).mp3 |
And so in theory, these things, I guess, could have developed independently of each other without having a common ancestor. But having a common ancestor is the best explanation of why we see these different processes. Some of these are quite complex or these different structures throughout life as we know it. And so yo... | Cellular evidence of common ancestry Natural selection AP Biology Khan Academy (2).mp3 |
And so you're saying, all right, I can maybe buy that, that there's this common ancestor right over here. But how do we construct this tree? How do we know when things branched off? Because some of these branches off of these trees, once again, these would have occurred hundreds of millions or billions of years ago, an... | Cellular evidence of common ancestry Natural selection AP Biology Khan Academy (2).mp3 |
Because some of these branches off of these trees, once again, these would have occurred hundreds of millions or billions of years ago, and none of us were around to observe that happening. And once again, that goes to more structural evidence. So for example, amongst what we now classify as eukaryotes, so everything i... | Cellular evidence of common ancestry Natural selection AP Biology Khan Academy (2).mp3 |
Membrane-bound organelles. These are things like a nucleus or mitochondria that we study in many other videos. They all have linear chromosomes. So in other groups in this tree of life, in this evolutionary tree, you might have circular chromosomes, but common to all eukaryotes are the linear chromosomes. And they all ... | Cellular evidence of common ancestry Natural selection AP Biology Khan Academy (2).mp3 |
So in other groups in this tree of life, in this evolutionary tree, you might have circular chromosomes, but common to all eukaryotes are the linear chromosomes. And they all have chromosomes that contain introns. Introns are sequences of DNA that don't code for genes that will then code into proteins. And we're still ... | Cellular evidence of common ancestry Natural selection AP Biology Khan Academy (2).mp3 |
Let me do this so they have a little brown-eyed baby here. And this is just something, I mean, there's obviously thousands of generations of human beings, and we've observed this. We've observed that kids look like their parents, that they inherit some traits, and that some traits seem to dominate other traits. And one... | Introduction to Heredity.mp3 |
And one example of that tends to be a darker pigmentation in maybe the hair or the eyes. Even if the other parent has light pigmentation, the darker one seems to dominate, or sometimes it actually ends up being a mix, and we've seen that all around us. Now this study of what gets passed on and how it gets passed on, it... | Introduction to Heredity.mp3 |
This was studied a long time, and kind of the father of classical genetics and heredity is Gregor Mendel, who was actually a monk. And he would mess around with plants and cross them and see which traits got passed and which traits didn't get passed, and try to get an understanding of how traits are passed from one gen... | Introduction to Heredity.mp3 |
So the first simplifying assumption I'll make is that some traits have kind of this all or nothing property. And we know that a lot of traits don't. Let's say that they're in the world, and this is a gross oversimplification. Let's say for eye color, let's say that there are two alleles. Now remember what an allele was... | Introduction to Heredity.mp3 |
Let's say for eye color, let's say that there are two alleles. Now remember what an allele was. An allele is a specific version of a gene. So let's say that you could have blue eye color or you could have brown eye color. That we lived in a universe where someone could only have one of these two versions of the eye col... | Introduction to Heredity.mp3 |
So let's say that you could have blue eye color or you could have brown eye color. That we lived in a universe where someone could only have one of these two versions of the eye color gene. We know that eye color is far more complex than that. So this is just a simplification. And let me just make up another one. Let m... | Introduction to Heredity.mp3 |
So this is just a simplification. And let me just make up another one. Let me say that, I don't know, maybe for tooth size, that's a trait you won't see in any traditional biology textbook. And let's say that there's one trait for big teeth, and that there's another allele for small teeth. And I want to make very clear... | Introduction to Heredity.mp3 |
And let's say that there's one trait for big teeth, and that there's another allele for small teeth. And I want to make very clear this distinction between a gene and an allele. I talked about Gregor Mendel, and he was doing this in the 1850s well before we knew what DNA was or what even chromosomes were and how DNA wa... | Introduction to Heredity.mp3 |
But let's go into the microbiology of it to understand the difference. So I have a chromosome. Let's say on some chromosome, let me pick some chromosome here, let's say I got that from my dad. And on this chromosome, there's some location here, we could call that the locus on this chromosome, that where the eye color g... | Introduction to Heredity.mp3 |
And on this chromosome, there's some location here, we could call that the locus on this chromosome, that where the eye color gene is. That's the location of the eye color gene. Now I have two chromosomes, one from my father and one from my mother. So let's say that this is the chromosome from my mother. And we know th... | Introduction to Heredity.mp3 |
So let's say that this is the chromosome from my mother. And we know that when they're normally in the cell, they aren't nice and neatly organized like this in a chromosome, but this is just to kind of show you the idea. And let's say these are homologous chromosomes, so they code for the same genes. So on this gene fr... | Introduction to Heredity.mp3 |
So on this gene from my mother, on that same location or locus, there is also the eye color gene. Now I might have the same version of the gene, and I'm saying that there's only two versions of this gene in the world. Now if I have the same version of the gene, I'm going to make a little shorthand notation. I'm going t... | Introduction to Heredity.mp3 |
I'm going to write big B, actually let me do it the other way. I'm going to write little b for blue, and I'm going to write big B for brown. There's a situation where this could be a little b and this could be a big B. And then I could write that my genotype, my genotype, I have the allele, I have one big B for my mom ... | Introduction to Heredity.mp3 |
And then I could write that my genotype, my genotype, I have the allele, I have one big B for my mom and I have one small b for my dad. Each of these instances or ways that this gene is expressed is an allele. So these are two different alleles. Or versions of the same gene. And when I have two different versions like ... | Introduction to Heredity.mp3 |
Or versions of the same gene. And when I have two different versions like this, one version from my mom, one version from my dad, I'm called a heterozygote or sometimes it's called a heterozygous genotype. And the genotype is the exact versions of the alleles I have. If I had, let's say, the lower case b, I had the blu... | Introduction to Heredity.mp3 |
If I had, let's say, the lower case b, I had the blue eye gene from both parents. So let's say that I was lowercase b, lowercase b. Then I would have two identical alleles. Both of my parents gave me the same version of the gene. And in this case, I'm called, this genotype is homozygous. Or this is a homozygous genotyp... | Introduction to Heredity.mp3 |
Both of my parents gave me the same version of the gene. And in this case, I'm called, this genotype is homozygous. Or this is a homozygous genotype. Or I'm a homozygote for this trait. Now you might say, Sal, this is fine. These are the traits that you have. This case, I have a brown from maybe my mom and a blue from ... | Introduction to Heredity.mp3 |
Or I'm a homozygote for this trait. Now you might say, Sal, this is fine. These are the traits that you have. This case, I have a brown from maybe my mom and a blue from my dad, in this case I have a blue from both my mom and dad. How do we know whether my eyes are going to be brown or blue? And the reality is that it'... | Introduction to Heredity.mp3 |
This case, I have a brown from maybe my mom and a blue from my dad, in this case I have a blue from both my mom and dad. How do we know whether my eyes are going to be brown or blue? And the reality is that it's very complex. It's a whole mixture of things. But Mendel, he studied things that showed what we'll call domi... | Introduction to Heredity.mp3 |
It's a whole mixture of things. But Mendel, he studied things that showed what we'll call dominance. Dominance. And this is the idea that one of these traits dominates the other. So a lot of people originally thought that eye color, especially blue eyes, was always dominated by the other trait. So we'll assume that her... | Introduction to Heredity.mp3 |
And this is the idea that one of these traits dominates the other. So a lot of people originally thought that eye color, especially blue eyes, was always dominated by the other trait. So we'll assume that here. But that's a gross oversimplification. So let's say that brown eyes are dominant. Dominant. And blue are rece... | Introduction to Heredity.mp3 |
But that's a gross oversimplification. So let's say that brown eyes are dominant. Dominant. And blue are recessive. I wanted to do that in blue. And blue eyes are recessive. If this is the case, and this is a, as I've said repeatedly, this is a gross oversimplification. | Introduction to Heredity.mp3 |
And blue are recessive. I wanted to do that in blue. And blue eyes are recessive. If this is the case, and this is a, as I've said repeatedly, this is a gross oversimplification. But if that is the case, then if I were to inherit this genotype, because brown eyes are dominant, remember I said the big B here represents ... | Introduction to Heredity.mp3 |
If this is the case, and this is a, as I've said repeatedly, this is a gross oversimplification. But if that is the case, then if I were to inherit this genotype, because brown eyes are dominant, remember I said the big B here represents brown eyes, and the lowercase B is recessive, all you're going to see for the pers... | Introduction to Heredity.mp3 |
Let me write this here. So genotype, and then I'll write phenotype. And genotype is the actual versions of the genes you have. And then the phenotypes are what's expressed, or what do you see? So phenotype. So if I get a brown eye gene from my dad, and I want to do it in brown, let me do it in brown so you don't get co... | Introduction to Heredity.mp3 |
And then the phenotypes are what's expressed, or what do you see? So phenotype. So if I get a brown eye gene from my dad, and I want to do it in brown, let me do it in brown so you don't get confused. So if I have a brown eye gene from my dad, and a blue eye gene from my mom, my color transitions aren't there. A blue e... | Introduction to Heredity.mp3 |
So if I have a brown eye gene from my dad, and a blue eye gene from my mom, my color transitions aren't there. A blue eye gene from my mom, because the brown eye is recessive, the brown eye allele is recessive. And I just said a brown eyed gene, but what I should say is the brown eyed version of the gene, which is the ... | Introduction to Heredity.mp3 |
Since the brown allele is dominant, I wrote that up here, what's going to be expressed are brown eyes. Now, let's say if I had it the other way. Let's say I got a blue eyed allele from my dad, and I get a brown eyed allele from my mom. Same thing, the phenotype is going to be brown eyes. Now, what if I get a brown eyed... | Introduction to Heredity.mp3 |
Same thing, the phenotype is going to be brown eyes. Now, what if I get a brown eyed allele from both my mom and my dad? Let me see. I keep changing the shade of brown, but they're all supposed to be the same. So let's say I get two dominant brown eyed alleles from my mom and my dad. Then what are you going to see? Wel... | Introduction to Heredity.mp3 |
I keep changing the shade of brown, but they're all supposed to be the same. So let's say I get two dominant brown eyed alleles from my mom and my dad. Then what are you going to see? Well, you could guess that. I'm still going to see brown eyes. So there's only one last combination, because these are the only two type... | Introduction to Heredity.mp3 |
Well, you could guess that. I'm still going to see brown eyes. So there's only one last combination, because these are the only two types of alleles we might see in our population, although for most genes, there's more than two types, for example, there's blood types, there's four types of blood. But let's say that I g... | Introduction to Heredity.mp3 |
But let's say that I get one blue allele from each of my parents, one from my dad, one from my mom. Then all of a sudden, this is a recessive trait, but there's nothing to dominate it. So all of a sudden, the phenotype will be blue eyes. And I want to repeat again, this isn't necessarily how the alleles for eye color w... | Introduction to Heredity.mp3 |
And I want to repeat again, this isn't necessarily how the alleles for eye color work, but it's a nice simplification to maybe understand how heredity works. And there are some traits that can be studied in this simple way. But what I wanted to do here is to show you that many different genotypes, so these are all diff... | Introduction to Heredity.mp3 |
So just by looking at someone's eye color, you didn't know exactly whether they were homozygous dominant. This would be homozygous dominant. Or whether they were heterozygotes. This is heterozygous right here. These two right here are heterozygotes. These are also sometimes called hybrids. But the word hybrid is kind o... | Introduction to Heredity.mp3 |
This is heterozygous right here. These two right here are heterozygotes. These are also sometimes called hybrids. But the word hybrid is kind of overloaded. It's used a lot. But in this context, it means that you've got different versions of the allele for that gene. So let's think a little bit about what's actually ha... | Introduction to Heredity.mp3 |
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