Question

Genes for blood-clotting proteins are on the X chromosome. The recessive allele produces a mutated blood clotting protein that results in “bleeder’s disease” or hemophilia, while the dominant allele produces the normal blood clotting protein. If a woman whose father had hemophilia marries a man whose blood clots normally, what is the genotype and phenotype ratio of their possible children

Answer 1

Genotype ratio = 1 X^hX : 1 XX : 1 X^hY : 1 XY

Phenotype ratio = 2 normal daughters : 1 affected son : 1 normal son

Step-by-step explanation:

Given that the father of the woman has hemophilia, the father must have transferred the allele for hemophilia (let us assume "h") to her. This makes the woman carrier for the disease (genotype = X^hX). The genotype of the normal man would be "XY".

A cross between carrier woman and normal man would obtain 2 normal daughters, 1 affected son and 1 normal son.

Genotype ratio = 1 X^hX : 1 XX : 1 X^hY : 1 XY

Phenotype ratio = 2 normal daughters : 1 affected son : 1 normal son