BIOL299 Lecture Notes - Lecture 16: Epistasis
15 Feb 2014
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9:3:3:1 phenotypic ratio expected if no gene interactions, i. e. phenotype of one locus does not affect phenotype the other locus. If the phenotype of one locus does affect the other locus, we get different ratios, which are derived by summing various classes from within 9:3:3:1: 9:7 (complementary gene action) e. g. purple flowers. Two phenotypic classes: genes act in the same pathway and. Either gene is sufficient; lof of both genes (aabb) is required for loss of normal end product: 9:3:4 (recessive epistasis) e. g. retriever coat color. Three phenotypic classes: genes act in the same pathway and. Both are required; lof in either gene blocks the production of a normal end product; some intermediates can be distinguished from each other, and e. g. aab_ can be distinguished from a_bb, but not from aabb.
