F13 lecture 13

E no dominance tends to produce normal bell shaped

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Unformatted text preview:   covariance among traits Evolu2on of quan2ta2ve characters •  Quan2ta2ve characters –  Show con2nuous (non- discrete) varia2on in nature •  Con2nuous: e.g. body size •  Meris2c: vertebral number, bristle number –  Inheritance paYerns indicate that varia2on in these traits is caused by several or many genes (“polygenic”) All genetic variation is discrete But most phenotypic traits are continuously varying Mendelian basis of con2nuous traits •  All gene2c varia2on is discrete •  But most phenotypic traits are con2nuously varying •  polygenic inheritance, when most loci are addi2ve (i.e. no dominance) –  tends to produce normal (bell- shaped) phenotypic distribu2ons –  the more loci, the smoother two locus, two allele system additive allele effects (=co-dominant, partial dominance intermediate dominance) capital alleles = long alleles lower case alleles = short alleles p =q = 0.5 all alleles/loci of equal effect genotype # long alleles frequency petal length AA BB 4 1/16 11 AA Bb 3 1/8 9.5 AA bb 2 1/16 8 Aa BB 3 1/8 9.5 Aa Bb 2 1/4 8 Aa bb 1 1/8 6.5 aa BB 2 1/16 8 aa Bb 1 1/8 6.5 aa bb 0 1/16 5 phenotypic value & genotypic value •...
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This document was uploaded on 02/27/2014.

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