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Unformatted text preview: is deﬁned as the allele with the highest homozygote ﬁtness • The parameter h measures the degree of dominance. If h = 0, then A1 is fully dominant (with respect to ﬁtness); if h = 1, then A2 is fully dominant, if h is between 0 and 1, the heterozygote has intermediate ﬁtness. • If h < 0 or h > 1, we have overdominance, or, underdominance, respec+vely. Industrial Melanism in the Peppered Moth Industrial Melanism in the Peppered Moth • Dark and light forms of the peppered moth, controlled by a single locus where the dominant form, C, indicates the dark form and the recessive homozygote, cc exhibits the light coloured phenotype. Genotype CC Cc cc Phenotype dark dark light Fitness on Light background 0.75 0.75 1 Fitness on dark background 1 0.67 1 • Observed changes in frequency during the industrial revolu+on in Britain appear to be concordant with these ﬁtness es+mates • Complica+ons with the story: the dark form is more common in areas where air pollu+on is absent; the dark form may have a viability advantage over the light form even in the absence of light and dark backgrounds Some Prac+cal Examples of Evolu+on by Natural Selec+on • Resistance to Warfarin in European rats (stable polymorphism of resistance and suscep+ble alleles is maintained) Some Prac+cal Examples of Evolu+on by Natural Selec+on • Drug‐resistant Plasmodium falciparum reduces the eﬃcacy of several an+‐
malarial drugs Some Prac+cal Examples of Evolu+on by Natural Selec+on • DDT resistance in many species of pests Some Prac+cal Examples of Evolu+on by Natural Selec+on • Mul+‐drug resistant Staphylococcus aureus (known as MRSA) – some strains are now resistant to all known an+bio+cs Some Prac+cal Examples of Evolu+on by Natural Selec+on • Rapid development of resistance to Myxoma virus in rabbits We are now at the end of sec+on 2. You should be able to: 2‐1) Describe game+c disequilibrium and the processes by which it arises 2‐2) Describe the inﬂuence of recombina+on on game+c disequilibrium and what forces operate to maintain GD in the face of recombina+on. 2‐3)Understand the deriva+ons of the equa+ons for D, D’ and Dmax. You should be able to: 2‐4) Calculate D, D’, Dmax and recombina+on rate,...
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