inheritance4

inheritance4 - More: Extensions of Mendelian Analysis...

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1 More: Extensions of Mendelian Analysis Last lecture: • http://www.esf.edu/efb/powell/inheritance3.pdf • Or go to my homepage, click on teaching, under Genetics click on inhertance3 Exam #2 in one week! Tuesday 10/16/07 Multiple genes affecting the same character example - hair color a lot of variation in mammals Multiple genes affecting the same character Many individual discontinuous traits if combined leads to a continuous trait much has been deduced by using mice as a model system at least 5 genes involved in mouse • more or less in other mammals • A, B, C, D, and S genes A gene determines the distribution of pigment on individual hairs allows Agouti hair coloration • salt and pepper appearance • good for camouflage yellow band A gene A_ - agouti (dominant over a) aa - black or solid color (recessive) other A alleles • A Y - all yellow (dominant over A) –homozygous lethal (A Y A Y ) ( pleiotropic) • a t - black and tan effect, lighter belly –recessive to A (A > a t > a series) B gene determines color of pigment B_ - black bb - brown
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2 Cross P AAbb (cinnamon) x aaBB (black) f 1 ? Cross P AAbb (cinnamon) x aaBB (black) f 1 all AaBb (agouti) Cross P AAbb (cinnamon) x aaBB (black) f 1 AaBb (agouti) x AaBb f 2 ? Cross P AAbb (cinnamon) x aaBB (black) f 1 AaBb (agouti) x AaBb f 2 9 A_B_ (agouti) 3 A_bb (cinnamon) 3 aaB_ (black) 1 aabb (brown) Cross P AAbb (cinnamon) x aaBB (black) f 1 AaBb (agouti) x AaBb f 2 9 A_B_ (agouti) 3 A_bb (cinnamon) 3 aaB_ (black) 1 aabb (brown) 9:3:3:1 ratio (typical dihybrid ratio)
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inheritance4 - More: Extensions of Mendelian Analysis...

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