Dr. smith's parents have normal hearing. however, dr. smith has an inherited form of deafness. deafness is a recessive trait that is associated with the abnormal allele d. the normal allele at this locus, associated with normal hearing, is d. dr. smith's parents could have which of the following genotypes? a) dd and ddb) dd and ddc) dd and ddd) dd and dd

The correct option is C) Dd and Dd

Explanation:

To explain the answer, lets make a punnet square with a cross between Dd and Dd.

       D       d

D     DD    Dd

d      Dd     dd

As deafness is a recessive trait, this means that both the alleles in a person should be same and recessive for that trait to occur in the phenotype. A cross between heterozygous carriers show that there will be a 25% probability that the offsprings produced will get the recessive alleles and hence they will be deaf. 50% of the offsprings will have the chance to be carriers like their parents. And there willbe a 25% chance that they will have normal homozygous alleles.