Epistasis


Epistasis involves two or more pairs of genes which are not alleles. One pair of genes, when having a dominant gene in that pair, will actually mask the other pair of genes.

For instance, a horse's coat color is controlled by many different gene pairs. A dominant B will give the horse a black color, and a b will give the horse a chestnut color. However, when a dominant Wis present in the second gene pair, the horse will be white no matter what. If the second gene pair is ww, then the horse will be the color of whatever the first gene pair is made of.

For example, the genotypes and phenotypes for horses are given for you to look at.

BBww = Black
Bbww = Black
bbww = Chestnut
BBWw = White
BbWw = White
bbWw = White


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