In-Depth Notes on Population Genetics and Selection

Population Genetics and Allele Fixation

• Probability of an allele being fixed in a population equals its frequency.
• As an allele frequency increases, the probability of its fixation also increases.
• Example: An allele starting at 50% frequency that gains an advantage will likely become fixed.

Richard Dawkins and the Selfish Gene

• Richard Dawkins is a prominent evolutionary biologist known for his book, The Selfish Gene.
• Focuses on genetic replication and the role of genes in evolution.
• Introduced concepts like gene-centered view of evolution.

Synonymous vs Non-synonymous Mutations

• Synonymous mutations do not change amino acid sequences, often neutral to selection.
• Non-synonymous mutations alter amino acids and can be subject to selection.
• The ratio of these mutations can indicate selection pressures.

Mutation Dynamics

• Synonymous mutations reflect mutation rates and population dynamics.
• Non-synonymous mutations can become fixed due to selection, reflecting beneficial mutations.
• Mutations can be categorized as beneficial, neutral, or deleterious.

Measuring Selection

• Increased non-synonymous mutations suggest selection acting on those genes.
• Low heterozygosity indicates a lack of genetic variation; useful for measuring selection.

Genetic Hitchhiking

• Neutral alleles can be carried along with beneficial alleles due to their close proximity on chromosomes.
• Linkage between genes affects how often they recombine; beneficial alleles can pull neutral alleles along.

Equilibrium and Genetic Linkage

• The concept of allelic equilibrium, whereby allele combinations should occur with equal frequencies in a population unless influenced by selection.
• If short distances separate genes, they may show linkage disequilibrium due to selection pressures.

Measuring Selection Across Populations

• Comparing mutation rates within populations and between species provides insights into historical selection events.
• Data from many species can help to understand evolutionary processes and fixation events.

Null Hypothesis and Allelic Combinations

• The null hypothesis suggests allele combinations are equally frequent in the population.
• Deviations from this hypothesis may indicate selection dynamics affecting alleles.

Selection Impact on Allelic Frequencies

• Even if genes are not linked, environmental and selection pressures can influence allele frequency.
• Unfavorable combinations may be eliminated from the population due to negative selection, impacting observed frequencies.

Recap on Selection Dynamics

• Understanding how selection impacts allele combinations and frequencies is crucial for studying population genetics.
• Multiple factors, including mutation rates and recombination events, interact to shape genetic diversity.