Pop Size Matters
- Genetic Drift
- It is basically random sampling of alleles in the subsequent generation
- Using a mathematical model, it has been show that an average of 4N generations (N = population size) are required for an allele to get fixed in that population
- Infinite Mutaion model (measure of increase of allels) and Stepwise mutation model (in/decrease of alleles in a pop),. often used to measure the loss of allles (Drift) in a population
- Importance of linkage
- Linkage plays an impo role. Deleterious genes are selected in linked status, while lost in unlinked status
- Genetic Draft
- Reduced efficiency of selection on a linked loci=> Hill-Robertson Effect
- Selective sweep (or hitchhiking effect) is the reduction or elimination of variation among the nucleotides in neighbouring DNA of a mutation as the result of recent and strong natural selection.
- Effective population size: is the inbreeding effective pop size
- Relationship between effective and actual size: They are proportional, but effective pop size gets reduced with more of selective sweeps
- Population size:
- Pop size inversely proportionate to to the body size
- Higher Mutation rates:
- Genome size is +vely correlated with the base-substitution rate
- Genome size is -vely correlated with the recombination rate
- Effective pop size:
- Within species allelic diversity (basically the subtitutions per silent site) is more in prokaryotes (more pop size and less genome size) compared to vertibrates
- Sources of Bias:
- Nucleotide heterozygosity
- Mutation
- Mismatch repair mechanisms
- Resolution of Paradox variation
- EPS vary between larger and smallest organisms atleast to 5 order
- Mutationas a Weak selective force
- Alleles of more complexity will be more suceptible to mutation
- Genome size is inversely correlated with silent site mutation