es at the expense of the other

es at the expense of the other - A allele pairs with...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
es at the expense of the other. Fine if we believe that environments are ~constant over time (maybe they are in the intestine) and that alleles with different fitnesses can be considered outside the context of the entire genotype. Probably unrealistic for many haploids (and most diploids). In diploids a bit more difficult: is it the phenotype, genotype or allele that determines fitness. Well it is all: selection acts on phenotype which is produced by a genotype in a given environment leading to the change in allele frequencies which in the next generation gives different genotype frequencies. Problem: neither genotype or phenotype are inherited intact (phenotypic "inheritance" depends on heritability of trait VG/VP ) One approach is to determine fitness of alleles e.g. " average excess " of allele: p' = (p 2 w AA + pqw Aa ) / (p 2 w AA + 2pqw Aa + q 2 w aa ) = [p (pw AA + qw Aa )] / (p 2 w AA + 2pqw Aa + q 2 w aa ) where pw AA + qw Aa = w A = fitness of A allele. Thus p' = p Think about it: this is the frequency with which the
Background image of page 1
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: A allele pairs with itself (the A allele) resulting in fitness w AA plus the frequency with which the A allele pairs with the a allele resulting in fitness w Aa relative to (i.e., divided by) the average fitness in the population (wbar). This is a very nice formula since the ratio w A /wbar determines whether p will increase or decrease in the next generation. Fitness (selective) values of genotypes are a similar thing since they average the interaction effects of the AA genotype over all other genotypes at all other loci in the genome for a given environment: average fitness of AA when coupled with the B locus: (w AA = p 2 w AABB + 2pqw AABb + q 2 w AAbb ) assuming p=f(B) and q=f(b). Note: selection will continue until: w A = wbar (i.e., the ratio is = 1.0 and p' = p(1), no change). Thus average fitness in the population will be maximal but this does not mean the fitness of the population is maximal....
View Full Document

This note was uploaded on 11/05/2011 for the course BIOLOGY MCB2010 taught by Professor Jessicadigirolamo during the Fall '10 term at Broward College.

Ask a homework question - tutors are online