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High school biology
Example punnet square for sex-linked recessive trait
Example punnet square for sex-linked recessive trait.
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Isn't there a 25% chance of there being a hemophiliac daughter because there are 4 offspring options... and only ONE of them is a hemophiliac girl?(10 votes)
The question asks "What is the percent chance that SHE will have hemophilia", implying that the offspring will be a daughter, and out of the 4 offsprings only 2 are daughters. So since one daughter will be hemophiliac and the other won't, there is a 50% that the daughter will be hemophiliac.(9 votes)
- I am confused as why it is 50% instead of 25% because its 1/4 chance of daughter having it?(4 votes)
It is 50% chance that a daughter has hemophilia because the question is what percent chance a daughter has it, so out of the two possible genotypes for a girl, one of them will be a carrier of hemophilia and the other will exhibit the disease, making it a 50% or 1/2 chance. Now draw a punnett square. If this hemophiliac daughter were to have children with a non hemophiliac man, all their daughters would be carriers and their sons would all have hemophilia. If she were to have children with a hemophiliac man, all their children would exhibit hemophilia. Hope this helps. :)(6 votes)
- If a female heterozygous recessive for hemophilia mates with a normal man and has 4 children, what are the possible genotypes and phenotypes expected in these offspring? *How many offspring do you expect to have hemophilia? **What sex of the offspring is affected?(3 votes)
If the Father does not have hemophilia and the Mother is heterozygous for the disease there is a 25% chance that the offspring will have hemophilia, that offspring would be a boy because the girl needs two X chromosomes with hemophilia. Put it on a punnet square(3 votes)
- Hi
What would happen in the case that the X-linked trait is dominant?
Does that mean all of the offspring would display the dominant allele and none display the recessive allele?
Thanks :)(3 votes)
If the X-linked trait is dominant would that mean that every offspring in every generation would display the dominant allele as every offspring has at least an X-chromosome, women have 2 and men have 1 and because it's dominant, it would be expressed in the phenotype for every offspring. However, it also depends on the parents. If the parents is homozygous for the dominant allele every offspring would be expressed in the phenotype, no matter what the dad would have for genotype, as every offspring would be needed to inherite at least 1 of the alleles from the mom, and as both are dominant, every offspring would also have the dominant allele. However, if the mom would be heterzygous for the dominant allele, it would also have a copy of a recessive allele, and if the dad would be healthy with a recessive allele, there's a 50% chance of the offspring getting the dominant allele. If the mom instead would be homozygous for the recessive allele and we have a healthy dad not carrying the disease, every offspring wouldn't display the dominant allele. But however, if the dad had the dominant allele and we had a healthy mom being homozygous for the recessive allele, every daughter would get the disease, as every daughter need to inherite 1 X-chromosome form the dad, where the dominant allele is sitting on. Every son would instead be healthy, as they only get the Y-chromosome from the dad, where the dominant allele isn't sitting on and an X-chromosome from the mom where there isn't any allele expressing this disease in this case.(2 votes)
- what would happen if the x chromosome is dominante(2 votes)
In females, dominant X-linked mutations will always cause the disorder. This is because the mutated gene takes over or overrides the genes on the healthy X chromosome. In males, there's only 1 X chromosome and if it has the dominant mutation, they'll have the disorder.(2 votes)
- What is the mutation that causes hemophilia?(2 votes)
- Hemophilia is an X-linked recessive disorder that exists in two forms, hemophilia A and hemophilia B. Hemophilia A is characterized specifically by a mutation on the factor VIII gene of the X, whereas hemophilia B is caused by a mutation on the factor IX gene of the X chromosome.(2 votes)
how do I know which is dominant or un dominant(2 votes)- The small letter is the recessive, or un dominant trait and the dominant trait is the capital letter. In this case, the non hemophiliac allele, the H, is the dominant allele and the hemophiliac allele, the h, is the recessive allele. There are other diseases called X-linked dominant diseases, I'm sure you can find a video on it. Hope this helped. :)(2 votes)
- hemophilia is nas x-linked recessive trait that affects blood clotting. if a carrier woman and a hemophiliac man have a daughter, what is the percent chance that she will have hemophilia ?(2 votes)
50%. Out of the two possible daughter genes, one codes for hemophilia and the other codes for without. Therefore, the percent chance is 1/2 = 50%.(1 vote)
sn't there a 25% chance of there being a hemophiliac daughter because there are 4 offspring options... and only ONE of them is a hemophiliac girl?(2 votes)- How do I get the phenotype and genotype ratio?(2 votes)
Video transcript
- [Instructor] Hemophilia is
an X-linked recessive trait that affects blood clotting. If someone has hemophilia, their
blood has trouble clotting. If a carrier woman and a
hemophiliac man have a daughter, what is the percent chance
that she, the daughter, will have hemophilia? So, if you're so inspired,
pause this video, and try to work through this on your own. All right, now let's work
through this together. And to do this, let's
think about the genotypes of both the mother and the father. So, let's start with the mother. And since it is an
X-linked recessive trait, we're going to be dealing
with the sex chromosomes. So, let's just remind
ourselves that the mother, because she's female, is going to be XX, have two X chromosomes. The father, the father is going to
have an X chromosome and a Y chromosome. But now let's think about the hemophilia. They say it's a carrier woman. So, a carrier woman means that
one of her two X chromosomes would have the hemophilia allele, and the other one wouldn't. Carrier implies that she
doesn't show the trait. She doesn't have hemophilia,
but she's carrying one of these X-linked recessive hemophilia alleles. So, we could say that
one of her chromosomes, one of her X chromosomes
does not have hemophilia. I use capital H for the dominant allele, which you would say is no hemophilia. We tend to use the
capital for the dominant. And then the lowercase h, well, this would be the X chromosome that has the hemophilia allele. And I did it lowercase h
because it is a recessive trait. And so this is hemophilia. And now, what about the father? Well, it's X-linked, and the father only has one X chromosome. And they say it's a hemophiliac man. And so that one X chromosome is going to have the hemophilia allele. And so the reason why
he exhibits hemophilia is that there is no other X chromosome with the dominant allele to be dominant over the hemophilia allele. But now let's cross these
two with a Punnett square. So, the father to the
offspring could contribute the X chromosome that
has the hemophilia allele or a Y chromosome. And the mother can
contribute the X chromosome that doesn't have the hemophilia allele or the X chromosome that does
have the hemophilia allele. And now I'll draw my
little Punnett square here. So, there you go. And so what are the different scenarios? Well, this top-left scenario
would be I get the X chromosome from the mother that does not
have the hemophilia allele, and I get the X chromosome from the father that does have the hemophilia allele. This scenario is the X
chromosome from the mother with the hemophilia allele
and the X chromosome from the father with
the hemophilia allele. This scenario is the X
chromosome from the mother without the hemophilia
allele, so no hemophilia, or with the non-hemophilia allele, and the Y chromosome from the father. And this is the X
chromosome from the mother that has the hemophilia allele and the Y chromosome from the father. Now, what is the percent chance that she, that a daughter would have hemophilia? So, which of these
scenarios show a daughter? Well, the daughters are
going to be the XX scenarios. So, these are the two scenarios in which they have a daughter. These two, because there's a Y chromosome, these would be them having a son. So, out of the two scenarios
where they have a daughter, one of those scenarios you have two of the recessive alleles. And so this is a situation
where you have a daughter, daughter with hemophilia, hemophilia, right over here. And so, if we know they have a daughter, what is the percent chance
that she will be a hemophiliac? Well, one out of two, so there is a 50% chance. Now, what's useful about
this Punnett square is you could answer
all sorts of questions. You could say what is the percent chance that they have a hemophiliac son? Well, one out of these four
scenarios is a hemophiliac son. Then you would say there's a 25% chance that they have a hemophiliac son. Similarly, there is a 25% chance that they have a non-hemophiliac son. If someone said what is the percent chance that they have a hemophiliac offspring? Well, that would be these two
scenarios right over here. So, two out of the four scenarios
are hemophiliac offspring, so that would be 50%. If you said, given that they had a son, what is the percent chance that
they don't have hemophilia? Well, you would say, given
that they have a son, so that would be those two scenarios, one out of those two scenarios, the son does not have hemophilia. So, that would again be a 50%. So anyway, hopefully this was useful.