Question

A couple is planning to have children. The father is affected by an autosomal dominant disease, but the mother does not have the disease gene. If the father is a heterozygote, what is the chance that their first child will be affected by the autosomal dominant disease?

A. 100%
B. 75%
C. 50%
D. 2596

Answer 1

C. 50%

Step-by-step explanation:

Let's assume that the dominant allele "A" is responsible for the disease while the recessive allele "a" gives normal phenotype. The genotype of the affected heterozygous father would be "Aa" and the genotype of the normal mother would be "aa". A cross between Aa x aa would give progeny in the following ratio= 1/2 Aa (diseased): 1/2 aa (normal). Therefore, there are 1/2 or 50% chances for this couple to have a child affected with the autosomal dominant disease.