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Unformatted text preview: n is the mean ﬁtness as determined by all loci, and u is the average mutaKon rate €
over all loci, and n is the number of loci. • See page 215 for the derivaKon of the drop in mean ﬁtness due to the load across all loci: w n ≅ 1 − Ln
≅ 1− U U – the number of deleterious mutaKons per zygote • EsKmates from primates (Eyre‐Walker and Keightley) were found to be surprisingly high • In order to avoid accumulaKon of deleterious mutaKons, every new mutaKon must be eliminated by geneKc death (or a failure to reproduce) • If U = 3, as esKmated for humans in one study, then each individual must suﬀer three geneKc deaths if the populaKon is to avoid meltdown! • Something is clearly wrong… SynergisKc Epistasis • EsKmates of U suggest that mean ﬁtness of populaKons is much lower (even negaKve – see p. 214!) than reality • This is probably because our assumpKon of mulKplicaKve interacKons is unrealisKc • Kimura and Maruyama (1966) suggested the idea of ‘synergisKc epistasis’ to understand how deleterious mutaKons interact to impact organismal ﬁtness • Under their model, each deleterious mutaKon has an impact on ﬁtness which is greater than the previous mutaKon (e.g. eﬀect on ﬁtness increases exponenKally) • Thu...
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This note was uploaded on 11/20/2012 for the course BIO bio3124 taught by Professor Rezanokhbeh during the Spring '11 term at University of Ottawa.
- Spring '11