Genetics in Medicine

How are families counselled regarding recurrence risks of complex disorders?

Which of the following would be an appropriate part of a genetic counseling session?

A 30-year-old woman presents for genetic counseling. Her father died of Huntington disease. Given that 25% of people with an Htt mutation exhibit the disease at age 30, what is the likelihood that she carries the mutation?

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.

Given that the man in the preceding question is unaffected, what is the posterior probability that he carries an RB mutation?

A woman and her husband have a child affected with maple syrup urine disease (MSUD). The woman subsequently has an affair and becomes pregnant, but the father of this baby cannot be contacted for genetic testing. What information would be used to determine the risk of MSUD in the second child?

How is the posterior probability of a particular scenario of interest calculated?