University:
The University Of Western Ontario
Course:
Biology 2290F | Scientific Method in Biology
Academic year:

2022
Views:

76

Pages:

3
Author:

Kyuwon J.

Quantifying fitness Absolute Fitness (W): average number of surviving offspring for each genotype ● Relative Fitness (w): Divide offspring for a genotype by absolute fitness of the most successful genotype (most successful genotype will always have w=1, all others < 1) ● ● wAA < wAa > waa heterozygote advantage wAA = waa > wAa heterozygote disadvantage ● Dominance status of an allele that is not related to fitness does not affect its frequency over time Dominance status of an allele that is related to fitness affects its frequency over time ○ Selection against a dominant allele: allele will be removed from the population ○ Selection against a recessive allele: frequency of recessive allele decreases but it never disappears completely; it can hide in heterozygotes Absolute Fitness (W): average number of surviving offspring for each genotype ● ● ● Relative Fitness (w): Divide offspring for a genotype by absolute fitness of the most successful genotype (most successful genotype will always have w=1, all others < 1) ● ● wAA < wAa > waa heterozygote advantage wAA = waa > wAa heterozygote disadvantage ● Dominance status of an allele that is not related to fitness does not affect its frequency over time ● Dominance status of an allele that is related to fitness affects its frequency over time ○ Selection against a dominant allele: allele will be removed from the population ○ Selection against a recessive allele: frequency of recessive allele decreases but it never disappears completely; it can hide in heterozygotes Heterozygote advantage ● Heterozygote Advantage ○ Allele frequencies will stabilizes near 0.5 ○ Once frequencies stabilize, selection is still occurring but evolution is not ○ Genetic variation maintained Heterozygote disadvantage ○ More common allele frequency increases to 1, less common allele vanishes ○ Rare allele disappears not because it’s harmful, but they are most likely to be found in heterozygotes ○ Genetic variation decreases Genetic Drift vs Non- random mating ● Genetic Drift ○ Random sampling error that occurs in small populations ■ Allele frequencies change due to chance ● ○ Over many generations, one allele may completely disappear ○ Decreases genetic variation by making alleles more/less common Non-Random Mating - changes genotype frequencies but not allele frequencies