Fox Terriers, homozygous for the recessive alleles of a particular gene, are blind from birth.

Fox Terriers, homozygous for the recessive alleles of a particular gene, are blind from birth. A pair of sires with a normal phenotype produced seven puppies, of which five were of the normal phenotype and two were blind. Establish the genotypes of the parents and their offspring.

Let us designate the gene that, under the condition of its homozygous representation, the development of blindness in fox terriers, as c, then the corresponding gene for normal vision will be C.

Blind puppies – cc. Such puppies can appear only from two dogs that have recessive genes in their genotypes, albeit in a latent form. Since the parental individuals have normal vision, it should be concluded that they are both heterozygous for the trait in question.

Fox Terriers – Parents will be Cc. Such individuals produce C and c germ cells.

Possible offspring from such dogs:

puppies with normal vision (CC, Cc) – 75%;

blind puppies (cc) – 25%.

The resulting splitting among the offspring of these fox terriers satisfies the probability we obtained (5: 2).