The Genetics of German Cockroaches: Linked Genes and Gametes

Understanding Linked Genes in German Cockroaches

In German cockroaches, bulging eyes (bu) are recessive to normal eyes (bu+), and curved wings (cv) are recessive to straight wings (cv+). These traits are encoded by autosomal genes that are linked to each other.

The Given Scenario

A specific cockroach has the genotype bu+ bu cv+ cv, with the genes being in repulsion. This means that the dominant allele of one gene is linked to the recessive allele of another gene, and vice versa.

The Question

Which set of genes will be found in the most common gametes produced by this cockroach?

(A) bu+ cv+

(B) bu cv

(C) bu+ bu

(D) cv+ cv

(E) bu cv+

Answer: (E) bu cv+

Explanation: Since the genes are in repulsion, the parental type gametes will have the combinations bu cv+ and bu+ cv. In linked genes, parental gametes appear in higher numbers than recombinant gametes. Therefore, the most common gametes produced by this cockroach will have the genes bu and cv+.