00:01
Hello, so let's answer now the question.
00:02
So here we have two pedigrees and each pedigree is asked if this is a pedigree that shows or each of the pedigree shows an x -linked recessive trait.
00:19
Okay, so this is about the x -linked recessive.
00:32
Take note that in the pedigree, the box is the male, the circle, is the female and if it is shaded then it is affected but if it is not shaded then it is normal it is either a carrier or has no the has no x -linked allele okay or no recessive allele carried now take note that for males okay for males if the genotype is x y then if the x is somehow affected then the males is affected already because take note males only have one x if the x is affected with the trait then the entire male is already affected and if this is the genotype of the male the x is not affected and the male is normal for females okay since females have two x's so if both of the x has the trait then the female is affected if the female has only one affected x and the other x is normal then the female is normal but a carrier and if the x if both x are normal then the female is normal and not a carrier normal and not carrier so let's go to the first box so here we see that the male or the female is affected so therefore the genotype of this female is xx both x are affected so this affected x comes from the mother and the father so here the mother should be a carrier because the picture is showing to us that it's normal but if we will put x that is affected to the father and in the box shows to us that the father is normal because it is not shaded therefore this assumption is wrong or this pedigree is not showing to us an x -link recessive trait because if the father or if this trait is x -link recessive trait, the father should be affected and the mother should be a carrier so that this daughter can be affected.
03:42
But since the father is not affected, therefore this is just an autosomal recessive trait.
03:49
So therefore, our answer here for the first pedigree is we have no.
03:56
So for the first pedigree, our answer is we have no.
04:02
This is a not a pedigree for an x -linked recessive trait but it is a pedigree of an autosomal recessive trait okay so we cannot put this one okay let's proceed to the next planet square here we see that the male is affected so let's assume that it is an x a linked uh recessive trait so let's put x okay x y so the x is affected that's why the male is affected now, since the x here comes from the mother, so the mother should be carrier because it says here that the mother is normal and the father is affected.
04:51
But anyway, whether the father is affected or not, it doesn't matter because if the offspring is male and it carries the disease or the trait, the x came from the mother, not from the father...