Population Genetics

Gene

DNA sequence coding for RNA/protein; found at a locus.

Alleles

Different gene variants.

Diploid organisms

Organisms that have two copies of each gene.

Homozygous

Genotype with identical alleles.

Heterozygous

Genotype with different alleles.

Gene pool

All alleles in a population.

Genotype

An individual’s allele combination.

Phenotype

Observable traits.

Population

Group of the same species in a shared environment that can interbreed.

Polymorphism

The presence of two or more alleles at a frequency greater than 1%.

SNPs

Single Nucleotide Polymorphisms, a major source of genetic variation.

Hardy-Weinberg Equation

Mathematical model for allele and genotype frequencies in a population.

Hardy-Weinberg equilibrium conditions

No mutations, no natural selection, large population, no migration, random mating.

Microevolution

Changes in a population’s gene pool over generations.

Natural Selection

Beneficial heritable traits become more common over generations.

Adaptation

Evolutionary changes improving survival and reproduction.

Reproductive Success

Likelihood of contributing fertile offspring.

Fitness

Relative reproductive success of a genotype.

Directional Selection

Selection that favors one extreme phenotype.

Stabilizing Selection

Selection that favors intermediate phenotype, against extremes.

Disruptive Selection

Selection that favors both extremes, not intermediates.

Balancing Selection

Maintains genetic variation through balanced polymorphism.

Intrasexual Selection

Same-sex competition for mates/resources.

Intersexual Selection

Mate choice based on traits signaling genetic quality.

Sexual Dimorphism

Visible differences between sexes due to sexual selection.

Cryptic Female Choice

Female-driven mechanisms that influence sperm success in fertilization.

Genetic Drift

Random changes in allele frequencies, independent of fitness.

Bottleneck Effect

Dramatic population reduction followed by recovery.

Founder Effect

Small group separates from a larger population to establish a new colony.

Gene Flow

Movement of alleles between populations.

Assortative Mating

Similar phenotypes mate preferentially.

Disassortative Mating

Dissimilar phenotypes mate preferentially.

Inbreeding

Mating between genetically related individuals.

Inbreeding Depression

Reduced fitness due to increased homozygosity of harmful alleles.