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

Dihybrid

9:3:3:19:3:4

12:3:1

independent assortment

linkage

recessive epistasis

dominant epistasis

complementary action

redundancy

duplicate gene action

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