AP BIOLOGY

Detailed explanation-1: -In dogs, there is an hereditary deafness caused by a recessive gene, “d.” A kennel owner has a male dog (Gilbert) that she wants to use for breeding purposes if possible. The dog can hear. If the dog’s genotype is Dd, the owner does not wish to use him for breeding so that the deafness gene will not be passed on.

Detailed explanation-2: -3 Punnett Square. Since Gilbert can hear, his two possible genotypes are homozygous dominant ( DD ) and heterozygous ( Dd ). If after breeding there are any deaf puppies, his genotype is heterozygous ( Dd ). If there are none, his genotype is therefore homozygous dominant ( DD ).

Detailed explanation-3: -Hereditary deafness can be either cochleosaccular or neuroepithelial in origin. Cochleosaccular is the most common cause of deafness and is associated with coat color patterns. It is usually seen in dogs with the piebald color genes or merle color gene.

Detailed explanation-4: -If deafness is carried as a theoretical simple autosomal recessive gene (d), the breeding of two hearing carriers (Dd) (Table 1) will result, on average, in 25% affected dogs (dd), 50% hearing carriers (Dd), and 25% free of the defect (DD).

Detailed explanation-5: -Answer :-Female dog is heterozygous i.e. it has both recessive and dominant trait. Male dog is homozygous recessive i.e. it has both recessive traits.