A consultand comes to you for genetic counseling. His father and brother both had retinoblastoma. He himself has been unaffected. He and his wife are considering having children. What is the prior probability that he is a mutation carrier? Assume 90% penetrance for the disorder.

Question

Quizplus · Accepted Answer

Given that the consultand's father and brother both had retinoblastoma, it suggests an autosomal dominant inheritance pattern. Since the consultand has not shown symptoms, but has a direct family history, the prior probability that he is a carrier of the mutation (but unaffected due to incomplete penetrance) is 50%, assuming no other information is provided about the mother's health or genetic status.

A Consultand Comes to You for Genetic Counseling