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 dd
b. dd and dd
c. DD and DD
d. Dd and DD

The options are incomplete and have been listed incorrectly. Complete question has been attached.

C) Dd and Dd

Explanation:

It is given that deafness is a recessive trait which means that Dr. Smith has genotype dd since a recessive trait can only be expressed when both the alleles in genotype are recessive. However, his parents are normal. So his parents can have DD or Dd genotype. Dr. Smith has obtained one recessive d allele from his father and other recessive d allele from his mother. Thus, the parents should have Dd genotype and the correct option is c.

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