Question

Phenylketonuria is an inherited disease caused by a recessive autosomal allele. If a woman and her husband are both carriers, what is the probability that their first child will be a phenotypically normal girl? Phenylketonuria is an inherited disease caused by a recessive autosomal allele. If a woman and her husband are both carriers, what is the probability that their first child will be a phenotypically normal girl?

A. 3/8
B. 1/4
C. 1/16
D. 3/16

Answer 1

The ans will be
`(3)/(8)`

Step-by-step explanation:

As phenylketonuria is a recessive autosomal disease, and both the parents are carrier, so they both carry one defective gene and one good gene.

If they produced 4 children, the probability of diseased and non diseased child will be as follows.

diseased:
`(1)/(4)`

non diseased:
`(3)/(4)`

And the probability of male and female child will be
`(1)/(2)`.

So, the probability of phenotypically normal first girl child will be
`(3)/(4)` ×
`(1)/(2)` ⇒
`(3)/(8)`