Cystic fibrosis is a human recessive autosomal condition.If two heterozygous parents have two children, what is the probability that they will be born in the order: normal boy and affected girl?
A)3/64
B)3/512
C)9/512
D)9/256
E)3/16

Question

Quizplus · Accepted Answer

Each child has a 1/4 chance of being affected and a 3/4 chance of being normal. The probability of a normal boy is (3/4) * (1/2) = 3/8, and the probability of an affected girl is (1/4) * (1/2) = 1/8. The combined probability for the specific order is (3/8) * (1/8) = 3/64.

Cystic Fibrosis Is a Human Recessive Autosomal Condition