Being an X-linked trait, the genes determining color-blindness is carried by the X chromosomes. Since it is a recessive trait, all the X chromosomes of an individual should have the recessive allele before being expressed. Thus, females would need two copies of the allele as they have two X chromosomes. Males, however, would only need one as their sex chromosomes are made up of one X and one Y chromosome.
Color-blindness is an X-linked recessive disorder. Mike is color-blind. His wife, Meg, is homozygous for the normal color vision allele. Using Punnet squares, derive and compare the genotypic and phenotypic ratios expected for the offspring of this marriage.
If they have eight children, how many of them would you expect to be color-blind?
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