A plant of genotype CdCd is crossed to cDcD and an F1 testcr

A plant of genotype Cd/Cd is crossed to cD/cD and an F_1, testcrossed to cd/cd. If the distance between these two genes is 20 map units, the percentage of cd/cd F2 plants will be 40% will be cd/cd

Solution

Parents: Cd/Cd X cD/cD

F1 offspring: CD/cd X CD/cd

F2 offspring :

The f2 offspring produced are in 9:3:3:1 ratio.

The two genes Cd and cd form equal recombinants. If the two genes Cd and cd are 20 map units apart from each other, the percent of offspring with genotype cd/cd = 10%. This is because the cd is 10 m.u apart Cd. The geneotype cd/cd (10 x 2 = 20) = 20/2 = 10%

male/ female	CD	Cd	cD	cd
CD	CD/CD	CD/Cd	Cd/cD	Cd/cd
Cd	Cd/CD	Cd/Cd	Cd/cD	Cd/cd
cD	CD/cD	cD/Cd	cD/cD	cD/cd
cd	cd/CD	cd/Cd	cd/cD	cd/cd