A woman and man have approached you for genetic counseling and are concerned abo

ID: 135346 • Letter: A

Question

A woman and man have approached you for genetic counseling and are concerned about a hereditary form of deafness in their family. Both have normal hearing and there are no children. The woman's father has autosomal dominant sensory-neural deafness. Assume he is heterozygous. This hearing impairment displays onset at about age 10, and penetrance appears to be about 70%. There is no family history of deafness among the man's relatives. What is the probability that the woman is a carrier of the deafness allele?

Explanation / Answer

The woman’s father suffered with a dominant autonomous disease. That was in heterozygous condition. That means his daughter (the woman) does not contain any allele of the disease. If the daughter would contain the allele, she must be diseased.

Therefore, there are no chances of carrying the disease for the woman, because the disease will spread among offspring.

Answer is zero for the carrier of the allele.

Father Aa+XY x aa+XX Mother

Here A is the dominant allele for the disease and a is the

a + X

A + X

Aa + XX (Diseased daughter)

a+ X

aa + XX (Normal daughter)

A +Y

Aa + XY (Diseased son)

a + Y

aa + XY (Normal Son)