In fruit flies, an autosomal mutation in the gene for wing veining results in cross veinless wings. This mutation is recessive. At another gene, an autosomal recessive mutation results in white eyes. Which of the following indicates the genotype of an individual heterozygous at both loci?

A. CV+CV W + W

B. cv+cv w+w

C. v+v r + r

D. V+V R+R

B. cv+cv w+w

Explanation:

Fruit flies have a special nomenclature to write the genotype of individuals.

If the mutation is recessive, you have to write it with lowercase letter (s). If the mutation is dominant, you have to write it with capital letter (s). Wild-type alleles are indicated with a superscript plus (+).

In this problem, both crossveinless (cv) and white (w) mutations are recessive.

For that reason, a heterozygous individual's genotype for both genes will be written as:

cv⁺ cv w⁺ w