02-09-2007, 02:08 PM
Retinoblastoma usually occurs as a sporadic event but in around 10% of cases there is a positive family history due to autosomal dominant inheritance. In these families the penetrance is approximately 80% (= 0.8). A woman with retinoblastoma, whose father and grandfather were also affected, has an unaffected partner with no relevant family history. Which of the following is correct regarding their children?
a) The probability that their first child will be affected is 0.25.
b) The probability that their first child will be affected is 0.4.
c) The probability that each of their children will be affected is 0.5.
d) The probability that each of their children will be affected is 0.4 X 0.5.
a) The probability that their first child will be affected is 0.25.
b) The probability that their first child will be affected is 0.4.
c) The probability that each of their children will be affected is 0.5.
d) The probability that each of their children will be affected is 0.4 X 0.5.