A type of muscular dystrophy shows sex-linked recessive inheritance. Affected persons usually die by the age of 20. Suppose that a boy with the disease lives long enough to marry a woman heterozygous for the trait. If they have a son, what is the probability that he will have the disease?
A) 25%
B) 50%
C) 0%
D) 100%
E) 75%

Question

Quizplus · Accepted Answer

The disease is sex-linked recessive, meaning it is carried on the X chromosome. The affected father (X^dY) will pass his Y chromosome to his son, while the heterozygous mother (X^DX^d) has a 50% chance of passing the X^d chromosome. Thus, the probability the son will have the disease is 50%.

A Type of Muscular Dystrophy Shows Sex-Linked Recessive Inheritance