They dont have tails but they have blue eggs 30

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Unformatted text preview: ifactorial inheritance 31 Multifactorial inheritance – a phenotype arising from the action of two or more genes (polygenic), or from interactions between genes and the environment 32 Multiple gene interactions Most common traits are determined by more than one gene 33 Novel phenotypes can emerge from the combined action of the alleles of two genes e.g., comb shape in chickens 34 Comb Shape in Chickens Rose Walnut Pea Single 35 Individual traits can be determined by more than one gene Incomplete dominance, or 2 genes interacting? 36 Individual traits can be determined by more than one gene Phenotypic ratio 9:3:3:1 indicative of 2 genes responsible for comb shape acting independently in simple dominant and recessive manner Was thought to be a 1:2:1 ratio, 37 Two genes, acting on one trait (phenotype) 38 Notice: same phenotypic ratio as for dihybrid cross……. except only one trait (comb shape) is affected Here, two genes acting on two traits (phenotypes) Ratio of yellow (dominant) to green (recessive) = 12:4 or 3:1 Ratio of round (dominant) to wrinkled (recessive) = 12:4 or 3:1 39 Branching Pathway: F1 genotype = RrPp (all) F1 phenotype = All walnut F2 generation: RrPp x RrPp F2 phenotypic ratio for Rr x Rr 3/ R _ 4 1/ rr 4 F2 phenotypic ratio for Pp x Pp 3/ P_ 4 Combined F2 ratios 9/ R_P_ 16 1/ p p 4 3/ R_pp 16 3/ P_ 4 3/ rrP_ 16 1/ p p 4 1/ rrpp 16 = walnut = rose = pea = single 40 Complementary gene action Two or more genes can work in tandem, in the same biochemical pathway to produce a particular trait 41 Heterogeneous trait A mutation at any one of a number of genes can give rise to the same phenotype 42 Mutation in 2 different genes results in same phenotype The wild-type phenotype can be rescued by complementation 2 wrongs making a right N.B. wild-type allele is designated with superscript + -happens to be dominant in this case...
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This document was uploaded on 02/25/2014.

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