Since colorblindness is a sex-linked recessive trait:
A) fathers of all colorblind sons must be colorblind
B) fathers of all colorblind daughters must be colorblind
C) mothers of all colorblind daughters must be colorblind
D) mothers of all colorblind sons must be colorblind
E) all the sons of carrier females will be colorblind
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Since colorblindness is sex-linked that means that it exists on the X chromosome. Therefore, if a male has the gene, he will be color-blind. On the other hand, a woman must receive two copies of the gene on both of her X chromosomes to become color blind. This occurs because the ...
This job examines the notion that colorblindness is sex-linked.
For the problems attached please show the symbols used in human pedigree analysis and/or Punnett Square if needed. Please also explain answers. Thank you!
1. A sex-linked recessive allele c produces a red-green colorblindness in humans. A normal woman whose father was colorblind carries a colorblind man.
a. What genotypes are possible for the mother of the colorblind man?
b. What are the chances that the first child from this marriage will be a colorblind boy?
c. Of the girls produced by these parents, what proportion can be expected to be colorblind?
d. Of all the children (sex unspecified) of these parents, what proportion can be expected to have normal color vision?
2. Male house cats are either black or orange; females are black, orange, or calico.
a. If these coat-color phenotypes are governed by a sex-linked gene, how can these observations be explained?
b. Using appropriate symbols, determine the phenotypes expected in the progeny of a cross between an orange female and a black male.
c. Half the females produced by a certain kind of mating are calico, and half are black; half the males are orange; and half are black. What colors are the parental males and females in this kind of mating?
d. Another kind of mating produces progeny in the following proportions: ¼ orange males, ¼ orange females, ¼ black males, and ¼ calico females. What colors are the parental males and females in this kind of mating?
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