A maize of genotype CC dd is crossed to cc DD and an F1 test

A maize of genotype C/C; d/d is crossed to c/c; D/D and an F_1 test crossed to c/c; d/d. If the genes are linked, and 20 map units apart, the percentage of c/c: d/d recombinants will be 80 50 40 20 10 In Drosophila the tail, small wings, is controlled by an X-linked recessive allele. A small winged female is crossed to a normal mile If the F1 progeny are intercrossed, what proportion of the females in the F2 will be small winged? Choose the best answer. all will be small winged 1/4 2/3 1/2 3/8

Solution

10. recombinant frequency is 10%. map distance is 20mu indicates recombination frequency is 20%. as there are 2 recombinant gametes CD and cd, each constitute 10% of the population, while remaining gametes constitute 80%. Cd and cD have 40% each.

11. in females, 1/2 population is small winged. in the total population 1/2 are small winged which comprise males and females in 1:1 ratio, so 1/4 are female with small wings.

cross between small winged female and normal male: XsXs x XY

F1 is intercrossed

XsX x XsY

1:1:1:1 ratio small winged female:normal female:small winged male: normal male

	Xs	Xs
X	XsX	XsX
Y	XsY	XsY