So brown eyes and little teeth. So two are pink of a total of four equally likely combinations, so it's a 50% chance that we're pink. Very rare but possible. Which of the genotypes in #1 would be considered purebred. So these right there, those are linked traits. Well, the mom could contribute the brown-- so for each of these traits, she can only contribute one of the alleles. Other sets by this creator. Even though I have a recessive trait here, the brown eyes dominate.
When the mom has this, she has two chromosomes, homologous chromosomes. How is it that sometimes blonde haired people get darker hair as they get older? Want to join the conversation? Wasn't the punnett square in fact named after the british geneticist Reginald Punnett, who came up with the approach? And these are all the phenotypes. What's the probability of having a homozygous dominant child?
Let's say that she's homozygous dominant. And this grid that I drew is called a Punnett square. For example, you could have the situation-- it's called incomplete dominance. So this might be my genotype. In the last video, I drew this grid in order to understand better the different combinations of alleles I could get from my mom or my dad. But for a second, and we'll talk more about linked traits, and especially sex-linked traits in probably the next video or a few videos from now, but let's assume that we're talking about traits that assort independently, and we cross two hybrids. Or it could go the other way. Sorry it's so long, hope it helped(165 votes). Which of the genotypes in #1 would be considered purebred if every. So big teeth, brown-eyed kids. Well examining your pedigree you'd find out that at least one of your relatives (say your great grandmother) had blue eyes "bb", but when they had a kid with your "BB" brown great-grandfather, the children were heterozygous (one of each allele) and were therefor "Bb". So they're both dominant, so if you have either a capital B or a capital T in any of them, you're going to have big teeth and brown eyes, so this is big teeth and brown eyes. What are all the different combinations for their children? And so then you have the capital B from your dad and then lowercase b from your mom.
I could have this combination, so I have capital B and a capital B. Again your mother is heterozygous Brown eyed (Bb), and your father is (bb). And we could keep doing this over multiple generations, and say, oh, what happens in the second and third and the fourth generation? And I'm going to show you what I talk about when we do the Punnett squares. How is this possible if your Mom has Brown eyes, and your dad has blue, and Brown is dominant to blue? Let me draw our little grid. Two lowercase t's-- actually let me just pause and fill these in because I don't want to waste your time. Chapter 11: Activity 3 (spongebob activity) and activity 4 and 5 (Punnet Squares) Flashcards. This one is pink and this is pink. Now if we assume that the genes that code for teeth or eye color are on different chromosomes, and this is a key assumption, we can say that they assort independently. So it's 9 out of 16 chance of having a big teeth, brown-eyed child.
If you understand pedigrees scroll down to the second paragraph haha) A pedigree is basically a family tree with additional information about a (or a few) certain trait. Let's say you have two traits for color in a flower. But you don't know your genotype, so you trace the pedigree. So what we do is we draw a Punnett square again. Which of the genotypes in #1 would be considered purebred golden retriever. I didn't want to write gene. I don't know what type of bizarre organism I'm talking about, although I think I would fall into the big tooth camp. There I have saved you some time and I've filled in every combination similar to what happens on many cooking shows.
Isn't there supposed to be an equal amount? So these are all the different combinations that can occur for their offspring. And I looked up what Punnett means, and it turns out, and this might be the biggest takeaway from this video, that when you go to the farmers' market or you go to the produce and you see those little baskets, you see those little baskets that often you'll see maybe strawberries or blueberries sitting in, they have this little grid here, right there. Let me just write it like this so I don't have to keep switching colors. Well, you could get this A and that A, so you get an A from your mom and you get an A from your dad right there. But let's say that a heterozygous genotype-- so let me write that down. So let's say I have a parent who is AB. If you have them together, then your blood type is AB. There are 16 squares here, and 9 of them describe the phenotype of big teeth and brown eyes, so there's a 9/16 chance.
So, for example, to have a-- that would've been possible if maybe instead of an AB, this right here was an O, then this combination would've been two O's right there. Parents have DNA similar to their parents or siblings, but their body design is not exactly as their parents or kin.. Apparently, in some countries, they call it a punnett. So let's go to our situation that I talked about before where I said you have little b is equal to blue eyes, and we're assuming that that's recessive, and you have big B is equal to brown eyes, and we're assuming that this is dominant. Let's say the gene for hair color is on chromosome 1, so let's say hair color, the gene is there and there. It could be useful for a whole set of different types of crosses between two reproducing organisms. So let's say little t is equal to small teeth. What are the chances of you having a child with blue eyes if you marry a blue-eyed woman? Let's say your father has blue eyes. Actually, I want to make them a little closer together because I'm going to run out of space otherwise.
In terms of calculating probabilities, you just need to have an understanding of that (refer above). I had a small teeth here, but the big teeth dominate. They both express themselves. Sal is talking out how both dominant alleles combine to make a new allele. Hybrids are the result of combining two relatively similar species. For many traits, probably most, there are multiple genes involved in producing the trait so there is not a simple dominance/recessiveness relationship. So instead of doing two hybrids, let's say the mom-- I'll keep using the blue-eyed, brown-eyed analogy just because we're already reasonably useful to it. This results in pink. And remember, this is a phenotype. And I could have done this without dihybrids. And if I want to be recessive on both traits, so if I want-- let me do this.
This could also happen where you get this brown allele from the dad and then the other brown allele from the mom, or you could get a brown allele from the mom and a blue-eyed allele from the dad, or you could get the other brown-eyed allele from the mom, right? Since your father can only pass a "b", your eye color will be completely determined by whether your mom gives you her "B" or her "b". So this is a case where if I were look at my chromosomes, let's say this is one homologous pair, maybe we call that homologous pair 1, and let's say I have another homologous pair, and obviously we have 23 of these, but let's say this is homologous pair 2 right here, if the eye color gene is here and here, remember both homologous chromosomes code for the same genes. So the math would go.
Let me do it like that. It can occur in persons with two different alleles coding for different colours, and then differential lyonisation (inactivation of X chromosome) in different cells will produce the mosaic pattern, In simpler words, when there are two different genes, different cells will select different genes to express and that can produce a mosaic appearance. Maybe another offspring gets this one, this chromosome for eye color, and then this chromosome for teeth color and gets the other version of the allele. However, sometimes it is the other way around and the defective gene is dominant because it malformed protein will block the action of the correctly formed protein (if you have the recessive allele that works). And these Punnett squares aren't just useful. Let's say their phenotype is an A blood type-- I hope I'm not confusing you-- but their genotype is that they have one allele that's an A and their other allele that's an O. Hopefully, you're not getting too tired here. We have one, two, three, four, five, six, seven, eight, nine of those. Your mother has brown eyes, but your grandmother(mom's mom) had blue eyes.
1/2)(1/2) = 1/4 chance your child will have blue eyes. F. You get what you pay for. So if you said what's the probability of having a blue-eyed child, assuming that blue eyes are recessive? I want blue eyes, blue and little teeth. And let's say I were to cross a parent flower that has the genotype capital R-- I'll just make it in a capital W. So that could be the mom or the dad, although the analogy breaks down a little bit with parents, although there is a male and female, although sometimes on the same plant. These particular combinations are genotypes. Well, you have this one right here and you have that one right there, and so two of the four equally likely combinations are homozygous dominant, so you have a 50% shot. Called a genetic mosaic. Well, there are no combinations that result in that, so there's a 0% probability of having two blue-eyed children. So what is the probability of your child having blue eyes?
Well, we just draw our Punnett square again. AP®︎/College Biology. All of my immediate family (Dad, mum, brothers) all have blue eyes. Everybody talks about eyes, so I 'll just ask: My eyes are brown and green, but there is more brown than green... How is that possible?