Question

In the pedigree that is shown, which represents Irene's allele combination?

Answer 1

Irene could be either XHXH or XHXh. We know for a fact that she inherited at leasst one XH from her father, but there's a 50/50 chance of her inheriting an XH or and Xh from her mother

Answer 2

The red-green color blindness is a recessive X-linked trait. The females are not affected unless both the X chromosomes have the affected allele. Mostly, the females are the carriers, and the males are affected as they have only one X chromosome. In the given pedigree, the father of Irene have the normal allele, while her mother is a carrier. However, Irene is neither a carrier nor affected. This means that she carries normal alleles on both X chromosomes. Hence, her allele combination is $X^{H} X^{H}$ .