The farmer discovered that one bird was found in his flock with an undesirable trait that affects plumage.

The farmer discovered that one bird was found in his flock with an undesirable trait that affects plumage. It is known to be inherited as an autosomal recessive trait. How many birds in a herd of 8100 carry the unwanted gene?

Let’s designate the gene of an undesirable recessive trait as p, the corresponding dominant gene, which determines the desired plumage, will be designated as P.

The genotype of a bird exhibiting an undesirable plumage type will be written as pp, because it must be homozygous – consisting of two genes for the recessive trait p. Such a genotype could be formed only as a result of the fusion of the germ cells of two parent birds, each of which carried the unwanted gene p.

For the birth of a bird with a recessive phenotype, 2 parent individuals are required – heterozygotes Pp. Taking into account the born pp bird, which shows an undesirable trait in its appearance (pp), it can be argued for sure that 3 out of 8100 birds are carriers of unwanted genes.