Here is a genetic map: A 18 mu B 10 mu C . AAbbCC is crossed to aaBBcc to produce an F1 generation

Question

If you produce 1000 offspring from testcrossing the F1, what genotypes do you expect, and in what numbers? Assume that there is no interference.

Answer 1

There will be 8 possible genotypes, listed here as 4 pairs in the following order: double crossovers, A to B single crossovers, B to C single crossovers, and finally parental types. Every individual must receive a recessive allele of each gene from the tester strain.

AaBbCc You would expect 0.18 × 0.10 × 1000 = 18 total double crossovers, 9 for
aabbcc each of these two genotypes.

AaBbcc A to B crossovers should = 0.18 × 1000 = 180. Eighteen of these represent
aabbCc double crossovers, so A to B only = 180 - 18 = 162, 81 for each genotype.

Aabbcc B to C crossovers should = 0.10 × 1000 = 100. 18 of these represent
aaBbCc double crossovers, so B to C only = 100 - 18 = 82, 41 for each genotype.

AabbCc The two parental types together should be 1000 - 18 - 162 - 82 = 738.
aaBbcc Therefore, each parental type genotype should be 369.