A homozygous recessive with cd genes was crossed with dominant (+ +). If their hybrid is test crossed and the following result was obtained

+ +/cd	-900
cd/cd	-880
+d/cd	-115
c+/cd	-105

Than what will be the distance between genes c and d.

Recombination frequency = Number of recombinants/ total number of offsprings X 100 %. In the above example, number of recombinants =220; total number of offsprings = 2000. So 220/2000 X 100 = 11 map units. Hence distance between gene c and d is 11 map units.