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Gene Interaction

Gene Interaction. Types of Gene Interaction . Definition: coordinated action of non-allelic genes controlling a single phenotypic trait Type 1: simple unmodified Mendelian ratios Type 2: epistasis: modified Mendelian rations Type 3 Quantitative “polygenic” continuous variation (height).

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Gene Interaction

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  1. Gene Interaction

  2. Types of Gene Interaction • Definition: coordinated action of non-allelic genes controlling a single phenotypic trait • Type 1: simple unmodified Mendelian ratios • Type 2: epistasis: modified Mendelian rations • Type 3 Quantitative “polygenic” continuous variation (height)

  3. Epistasis • Definition: non-reciprocal interaction of non-allelic genes so that one gene masks the phenotypic expression of another non-allelic gene (opposite: pleiotropy) • Example Labrador Retrievers (E and B gene) EE/Ee BB/Bb • Dilute golden -> brown -> black pigment • E_B_ = black • E_bb = brown • eeB_ = golden • eebb = golden Altered ratio: 9:3:4 • Genotype ee is epistatic (standing above or masking remaining steps) to B_ • Geneotype B_ is hypostatic to ee http://www.steve.gb.com/images/science/recessive_epistasis.png

  4. Plumage in Parakeets (genes A and B) Gene A Gene B Blue + yellow White -> Blue (with gene A) White -> Yellow (gene B)

  5. Parakeets • If A is present and no B -> blue • If B is present and no A -> yellow • If B and A is present -> green • Neither (aa and bb) -> white pigment • Precursor is white for both A and B

  6. In horses http://courses.bio.psu.edu/fall2005/biol110/tutorials/tutorial5_files/figure_14_11.gif

  7. Mice http://www.zo.utexas.edu/faculty/sjasper/images/14.11.gif

  8. Kernel Anatomy http://www.fao.org/DOCREP/W0073e/p255.gif

  9. Pathways • Colorless 1 -> (gene A1catalyzes)-> colorless 2 • Gene A 2 catalyzes to bronze pigment • Gene Bz1 catalyzes to red pigment • Gene Bz2 catalyzes to purple pigment • Gene C and R must be present to active pathway • Gene CI inhibits action of A1 = 13:1 ratio • Gene rr inhibits A1 =9:7 ratio • Gene bz1 bz1 inhibits Bz2 = 9:3:4 • Gene a2a2 inhibits phenotypic expression of gene Y (yellow endosperm) 12:3:1

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