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Chromosome mapping and coefficient of coincidence

In the fruit fly, Drosophila melanogaster, a spineless (no wing bristles) female fly is mated to a male that is claret (dark eyes) and hairless (no thoracic bristles). Phenotypically wild type F1 female progeny were mated to fully homozygous (mutant) males and the following progeny (1000 total) were observed.


spineless 321
wild 38
claret, spineless 130
claret 18
claret, hairless 309
hairless, claret, spineless 32
hairless 140
hairless, spineless 12

(a) What are the map distances between the three genes? Draw the map.
(b) What is the coefficient of coincidence?

Solution Summary

Chromosome mapping can be done through F1 test cross results. In three point test sequence among genes as well as distance between genes in map units are calculated. Coefficient of coincidence tell us about double cross over.