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6.S: Genetic Analysis of Multiple Genes (Summary)

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    • The alleles of different loci are inherited independently of each other, unless they are genetically linked.
    • The expected phenotypic ratio of a dihybrid cross is 9:3:3:1, except in cases of linkage or gene interactions that modify this ratio.
    • Modified ratios from 9:3:3:1 are seen in the case of recessive and dominant epistasis, duplicate genes, and complementary gene action. This usually indicates that the two genes interact within the same biological pathway.

    Key Terms

    Mendel’s Second Law




    independent assortment


    recessive epistasis

    dominant epistasis

    complementary action


    duplicate gene action

    Orange, long, dilute, White masking, piebald spotting, calico

    This page titled 6.S: Genetic Analysis of Multiple Genes (Summary) is shared under a CC BY-SA 3.0 license and was authored, remixed, and/or curated by Todd Nickle and Isabelle Barrette-Ng via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.