BIOL-104 Lecture Notes - Lecture 2: Fecundity, Balancing Selection, Heterozygote Advantage
Document Summary
Witness- expected number of offspring over the courser of a lifetime. Fecundity- number of expected kids if they lie to adulthood. Absolute fitness expected number of offspring produced by a genotype. Relative fitness expected number of offspring produced by a genotype relative to the most fit genotype (most fit = 1, the rest are lower) Some alleles may increase survivorship but decrease fecundity or visa versa. So p" = (cid:894)f(cid:396)e(cid:395)ue(cid:374)(cid:272)y(cid:894)aa(cid:895)*(cid:396)elati(cid:448)e fit(cid:374)ess(cid:894)aa(cid:895)(cid:895) + (cid:894)0. 5 * f(cid:396)e(cid:395)ue(cid:374)(cid:272)y(cid:894)aa(cid:895)*(cid:396)elati(cid:448)e fit(cid:374)ess(cid:894)aa(cid:895)(cid:895) / ((frequency(aa)*relative fitness(aa)) + (frequency(aa)*relative fitness(aa) + (frequency(aa)*relative fitness(aa)) = amount of a / total number of offspring. Positive selection increases the frequency of a favorable allele in the population. Negative selection decreases the frequency of a harmful allele in the population. Balancing selection maintains an allele at some intermediate frequency between 0% and 100% Heterozygote advantage is one form of balancing selection there are always heterozygotes and they preserve the other alleles.
