Question

Phenylketonuria (PKU) is a disease that results from a recessive gene. Two normal parents produce a child with PKU. What is the probability that a sperm from the father will contain the PKU allele?

a. 2/3
b. 3/4
c. 1/3
d. 1/2
e. 1/4

Answer 1

d. 1/2

Step-by-step explanation:

According to this question, PKU (Phenylketonuria) is a recessive condition in humans. A normal human must possess at least a dominant allele in the gene.

In a situation where two normal parents produce a child with PKU. This means that both parents are heterozygous for the condition i.e Pp × Pp. Hence, the heterozygous male (Pp) will produce gametes in the following proportion: P (1/2) and p (1/2).

This means that the probability that a sperm from the father will contain the PKU allele (p) is 1/2 or 50%