Question

A fruit fly of genotype B R/b r is test-crossed with b r/b r. In 84 percent of the meioses, there are no chiasmata between the linked genes; in 16 percent of the meioses, there is one chiasma between the genes.

What proportion of the progeny will be BR/br?

Answer 1

In a test-cross between a fruit fly of genotype BR/b r and a fruit fly of genotype b r/b r, the proportion of progeny with the genotype BR/br is 16 percent, based on the given recombination frequency of 16 percent.

Step-by-step explanation:

In a test-cross between a fruit fly of genotype BR/b r and a fruit fly of genotype b r/b r, the recombination frequency between the linked genes is given as 16 percent. This indicates that there is one chiasma, or crossover event, between the genes in 16 percent of the meioses. The remaining 84 percent of the meioses do not have any chiasmata between the genes.

The proportion of progeny with the genotype BR/br can be calculated based on the recombination frequency. Since the recombination frequency is 16 percent, and recombination results in the production of non-parental genotypes, the proportion of progeny with the genotype BR/br would be 16 percent. The remaining proportion of progeny (84 percent) would have the parental genotypes BR and br.