Question

Different genes have been identified as causative for inherited forms of deafness. Because inherited deafness is a relatively rare characteristic in the population, individuals who are homozygous recessive for one gene that causes deafness are typically homozygous for functional alleles at other loci controlling the hearing phenotype. Knowing this, suppose a deaf man is homozygous for a recessive deafness allele on chromosome 17. He marries a deaf woman who is homozygous for a different recessive deafness allele on chromosome 3. What is the probability that they will have a child who is deaf due to either of these two mutated genes?

A. 100%

B. 75%

C. 50%

D. 25%

E. Closest to 0%

Answer 1

let the gene on the chromosome 17 be D and gene on the chromosome 3 be B, alleles of the gene D are D and d, D- dominant and d-recessive. alleles of gene B are B-dominant and b- recessive.

the genotype of the father is ddBB and genotype of the mother is DDbb

ddBB * DDbb

DdBb ( F1)

the F1 has normal alleles of both genes. so the F1 progeny is normal, so the answer is E) closest to 0%