In a chromosome region having the map A8B20D and a coefficie

In a chromosome region having the map A-8-B-20-D, and a coefficient of coincidence of 0.4, how many progeny of the phenotype A_bbdd will there be among 1000 progeny of the testcross ABD/abd times abd/abd?

Solution

Coefficient of coincidence = (observed DCO)/(expected DCO)

Expected Double Cross Over = 0.08 x 0.20 x 1000

= 16

0.4 = Observed DCO/16

6.4 = Observed DCO

There will be two double crossover. One of them is AAbbdd so it is 3.2 or 3