Answer:
3/8
Explanation:
Given that both the parents are carrier for phenylketonuria, the genotype of both parent is "Aa".
Probability of getting phenotypically healthy child = Aa x Aa = 3/4 Healthy (1/2 AA and 1/2 Aa) : 1/4 affected (aa).
Probability of getting a girl child = XY x XX = 1/2 girl (XX) : 1/2 boy (XY).
Hence, probability that their first child will be a phenotypically normal girl = 3/4 healthy x 1/2 girl = 3/8 healthy girl child.
