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#epistasis examples

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Gene intraction

An example of recessive epistasis is

Mouse coat color system involving C locus for tyrosinase pigment production and B locus for black versus brown exemplifies recessive epistasis. Genotype cc lacks tyrosinase, preventing melanin synthesis entirely, producing albino phenotype regardless of B- or bb genotype, thereby masking agouti brown variation. Meanwhile C-B- yields agouti, C-bb brown producing remaining visible classes. Combined albino class includes 3 ccB- plus 1 ccbb totaling 4, yielding 9:3:4 ratio. Sweet pea demonstrates 9:7 complementary, rice awn duplicate dominant, squash dominant epistasis, mouse illustrating suppleme

Ref: Cuénot and Castle, Early Mouse Genetics; Griffiths et al., Chapter 6: Mouse Coat as Recessive Epistasis Example

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Gene intraction

An example of duplicate dominant epistasis is

Rice awn character controlled by two loci where dominant allele at either locus promotes awn elongation via transcription factors activating cell elongation in parallel pathways. Biochemically either gene product suffices to trigger development. Cross heterozygous at both loci selfed produces 15 awned grains comprising 9 A-B- +3 A-bb +3 aaB-, and 1 awnless aabb, demonstrating diagnostic 15:1 duplicate dominant epistasis. This redundancy reflects selection during domestication where loss of one gene compensated by other. Pattern contrasts with squash dominant masking, sweet pea complementary bo

Ref: NCBI, Genetics of Rice Morphology; Griffiths et al., Chapter 6: Rice Awn Duplicate Dominant Illustration

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