In Drosophila the gene for eye color A wing shape B and body

In Drosophila, the gene for eye color (A), wing shape (B), and body color (C) are all found on the same chromosome. The following crossover frequencies for these genes were determined by experiments.

Genes

Crossover Frequency

A & B

12.5%

A & C

6.0%

B & C

18.5%

What is the correct sequence of the genes A, B and C on the chromosome?

Solution

Total crossover frequency = 12.5 + 6.0 + 18.5 = 37

Crossover frequency of gene A = 12.5 + 6 = 18.5 / 37 = 0.5

Crossover frequency of gene B = 12.5 + 18.5 = 31 / 37 = 0.83

Crossover frequency of gene C = 6.0 + 18.5 = 24.5 / 37 = 0.66

The correct sequence of genes on the chromosome is A . C and B.