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Biology LibreTexts

8: Gene Interactions and Epistasis

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    • 8.1: Epistasis and Other Gene Interactions
      Epistasis (which means “standing upon”) occurs when the phenotype of one locus masks, or prevents, the phenotype of another locus. Thus, following a dihybrid cross fewer than the typical four phenotypic classes will be observed with epistasis. As we have already discussed, in the absence of epistasis, there are four phenotypic classes among the progeny of a dihybrid cross.
    • 8.2: Example of Multiple Genes Affecting One Character
      Most aspects of the fur phenotypes of common cats can be explained by the action of just a few genes. Other genes, not described here, may further modify these traits and account for the phenotypes seen in tabby cats and in more exotic breeds, such as Siamese.