To help see the process write out the genotypes. The genes can be symbolized as follows:
b+ = gray body b = black body pr+= red eyes pr = purple eyes
Genotype of the heterozygous wild type (gray body and red eyes) using Morgan’s method:
The genotype of the homozygous recessive individual (used in a testcross) would be:
Determine the recombination frequency:
| 721 wild-type (gray-red) | 721/1566 = 46% | expected |
| 751 black-purple | 751/1566 = 48% | expected |
| 49 gray-purple | 49/1566 = 3% | recombinant |
| 45 black-red | 45/1566 = 3% | recombinant |
Total flies = 1566
(a) The percent recombination is therefore 6%
(b) Example: cross a wild type fly heterozygous for body color and wing shape with a fly homozygous recessive for the same traits (black body/curly wings)
