Population Genetics Flashcards
What is the equation for substitution rate?
SR = # differences/2t
Explain the difference between mutation and substitution
Mutation is a base pair change that introduces a new allele into the population
Substitution is a mutation that goes to fixation so the new allele is present in ALL individuals
How does mutation relate to drift and variation?
There is more variation with larger populations and higher mutation rates
Describe the situation if mutations are deleterious
Selection prevents them from drifting to high frequency
There is little variation and ALMOST no substitution
If population is very small and selection is weak substitution is possible
What happens if new mutations are advantageous?
Selection quickly drives them to high frequency and fixation
There is little variation and numerous substitutions
What are the three types of non-synonymous substitutions? Which is most common?
Deleterious - most common
Neutral
Advantageous
Explain the ratio of fixed to polymorphic sites
If the ratio is larger for non-synonymous sites are potentially under selection
The mutations that went to fixation go there faster without drifting for very long in the population
What is inbreeding? What does it do to allele frequencies?
Self fertilization that reduces observed heterozygosity
What are Fst and Fis?
Fst - inbreeding caused by divergence of Subpopulations relative to the Total
Fis - Inbreeding caused by assortative mating of individuals within the subpopulation
What is wrong with inbreeding?
It creates actual homozygotes as opposed to those expected under HWE
Rare deleterious recessive alleles wind up in homozygotes and reduce fitness instead of heterozygotes where they won’t harm
What are the advantages of inbreeding?
Mates are easier to find
Deleterious mutations are removed faster - exposed to selection
Mutation selection balance is lower
What are the advantages of outcrossing?
Produce more heterozygotes, create novel combinations of genes and reduces linkage disequilibrium
Can possibly remove deleterious mutations
Do novel gene combinations increase fitness?
It depends. It can create higher or lower fitness combinations. Recombination generates new variation for selection to act on
