Genes A B and C are linked on a chromosome and found in the

Genes A, B, and C are linked on a chromosome and found in the order A-B-C. Genes A and B recombine with a frequency of 7%, and genes B and C recombine at a frequency of 23%. For the cross a+b+c/abc+ x abc/abc, predict the frequency of progeny. Assume interference is 0.

Predict the frequencies of abc+, a+bc+, ab+c, a+b+c+, abc, a+bc, and ab+c+; answers should be to four decimal places.

Solution

The frequency of A and B recombination is 0.07

The frequency of B and C recombination is 0.23

The probability of double crossovers would be 0.23 x 0.07 = 0.0161 or 1.61%

Parental progeny: a b c+

Single crossovers between A and B : a+ b c (7%) a b+ c (7%)

Single crossovers between B and C : a+ b+ c+ (23%) a b c (23%)

Double crossovers: a+ b c (1.61%), a b+ c+ (1.61%)