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Unformatted text preview: 100% 0.0 0.5 AA Aa aa 1 2 1 0.0 0.25 AABB AaBB AABb aabb aaBb Aabb AaBb AAbb aaBB 1 4 1 4 6 0.0 0.25 1 15 1 15 6 20 6 Number of loci color Proportion of F2 offspring Aa x Aa: AaBb x AaBb AaBbCc x AaBbCc 1 2 3 100% No environmental variation With environmental variation BIO 320 Reading: Ch 2 pp 63-70 lecture 26 Ch 21.3 Ridley chapters 5, 6,7, X, 11, 21, 22 Problems: Question bank F & text 21.22-27 FINAL EXAM Thursday 5/15, 2:00 - 4:30 p.m. in Javits 100 Bring: photo ID - #2 pencil - calculator Quantitative genetics, complex traits & heritability- Inheritance at each locus is Mendelian. But the effects of many genes are considered at once. Polygenic inheritance : 1 trait governed by variation at many loci . Quantitative traits:- well defined , quantifiable ( metric ) character, with a continuous distribution in the population (contrast with discrete phenotypes for a single Mendelian gene) E.g.: height or birth weight in humans, or crop yield in plants.- continuous distribution due to contributions from variation at many genes , and from the environment.- frequent questions: what is the heritability of the trait, and how accurately can the phenotype of offspring be predicted from the parental phenotype?- huge economic significance; most agriculturally important traits (crop yield, animal weight) are quantitative. 1. Quantitative variation = Mendelian inheritance at many loci, + environmental effects Example: flower color. Assume alleles at many loci (A, B, C, D....) encode copies of a color-generating enzyme. Effects of alleles at each locus are additive : Equal contributions to color (no dominance) from each upper case allele (A, B, C, D...)....
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This note was uploaded on 06/03/2008 for the course BIO 320 taught by Professor N/a during the Spring '08 term at SUNY Stony Brook.
- Spring '08