Question

Mr Christopher is a colourblind and carrier for PKU.What %of sperms possesses defective allele for both?
0%
25%
50%
100%

Answer 1

0./. yes this the answer

Answer 2

Answer:

The correct answer should be 25%.

In humans, the allele for colorblindness is present on X chromosome.

In contrast, PKU (Phenylketonuria) shows autosomal inheritance as the alleles for the gene are present on the chromosome number 12.

As, Mr Christopher is a carrier for PKU, he must carry only one defective allele.

Thus, the probability of a sperm to carry the defective allele would be 1/2 or 0.5.

Now, we know that probability of a sperm to carry X chromosome (defective allele for colorblindness) is 0.5

Thus, the probability of a sperm carrying the defective alleles for both the disorder would be = 0.5 x 0.5

It comes out to be 0.25 that is, 25%.