To identify genes controlling coat color in Crumple-Horned Snorkacks, Luna Lovegood mutagenizes a pure-breeding line of wild type rainbow-colored Crumple-Horned Snorkacks, and screens the F2 generation for Crumple-Horned Snorkacks with altered coat color.
Four coat-color mutations, all of which are recessive to the wildtype are recovered: red (genotype r/r), yellow (genotype y/y), and two different whites, pearly white and glittery white (p/p and g/g). Crumple-Horned Snorkacks heterozygous for any one of these mutations (i.e., R/r, Y/y, P/p or G/g) are all rainbow-colored.
The following crosses are performed to determine whether these mutations are in the same gene or different genes. In each case, the F2 generation is produced by crossing F1 Crumple-Horned Snorkacks to each other. (Note that the F1 generation provides complementation data, but in a slightly different format.)
Cross Parental phenotypes F1 phenotypes F2 phenotypes
1 red X pearly rainbow-colored 9 rainbow-colored : 3 red: 4 white
2 red X glittery rainbow-colored 9 rainbow-colored : 3 red: 4 white
3 red X yellow red 3 red: 1 yellow
4 yellow X pearly rainbow-colored 9 rainbow-colored : 3 red: 4 white
5 yellow X glittery rainbow-colored 9 rainbow-colored : 3 yellow: 4 white
6 pearly X glittery rainbow-colored 9 rainbow-colored : 7 white
a. How many different genes controlling coat color have been identified?
b. Which pair(s) of mutations are in the same gene, if any?
c. What are the genotypes of the red and yellow Snorkacks in the F2 progeny from cross 3?
d. Are any of these mutations epistatic to another? If so, which? (state “allele X is epistatic to allele Y” in each case where it applies).
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