Question

You are working with two forms of progressive retinal atrophy (PRA) in dogs--one form in Siberian Huskies, which is a sex-linked recessive allele, and one form in Labs, which is an autosomal recessive. Each breed is normal for the disease allele in the other breed. Assume you mate a Siberian male with the disorder to a female Lab with the disorder. (Assume homozygosity for the normal allele.)

A) What is the phenotypic distribution of the progeny from this mating (include gender)?

B) What is the probability of a progeny with PRA from the inter se mating (both normal)?

C) From the results of the same inter se mating, what is the probability of having PRA given the pup is a male?

Answer 1

a)

Phenotype distribution is given as

2:2=1:1

XX^s=carrier serbian female

X^sX^L=Disorder

YY=Normal

X^LY=Disorder

b)

Probability of Progeny with PRA from intersemating is 50%

c)

The results of same inter se mating ,probability of having PRA given the pup is a male will be 25%=1/4