A gene on the Y chromosome causes a rare disease.A woman married to a man with the disease has three children.The first two are daughters without the disease.The third is a son.What is the probability that he will have the gene?

Question

Quizplus · Accepted Answer

The gene causing the disease is on the Y chromosome, which only males have. Since the father has the disease, he must have the gene on his Y chromosome. The son will inherit the Y chromosome from his father, so he will definitely have the gene.

A Gene on the Y Chromosome Causes a Rare Disease