Quiz 16: Risk Assessment and Genetic Counseling

Which of the following would be an appropriate part of a genetic counseling session? A) Tell the patient which genetic tests to have B) Advise them not to have an affected child C) Tell them what you would do in their situation D) Provide them with information E) A and D

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? A) Mutation rate for the MSUD genes B) Carrier frequency for MSUD mutations in the general population C) Carrier frequency for MSUD mutations in the appropriate ethnic population D) The risk can be calculated based on the mother's genotype alone E) The risk cannot be calculated with reasonable accuracy

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. A) 0 B) 10% C) 50% D) 90% E) Equal to the general population risk

Given that the man in the preceding question is unaffected, what is the posterior probability that he carries an RB mutation? A) 2% B) 5% C) 9% D) 10% E) 11%

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) 37.5% B) 43% C) 50% D) 57% E) 75%

How is the posterior probability of a particular scenario of interest calculated? A) Add all joint probabilities B) Determine the fraction of all joint probabilities that are accounted for by our scenario of interest C) Multiply all possible joint probabilities D) Add the prior probabilities E) Multiply the prior probabilities

How are families counselled regarding recurrence risks of complex disorders? A) Based on empirical recurrence risks B) Using Bayesian analysis C) Based on mutation rates for the gene D) Based on background incidence in the general population E) C and D