populationgenetic

Population genetics is the study of how and why allele frequencies in populations change over time. It seeks to understand the genetic structure of populations and the evolutionary processes that shape variation within and between groups.

The field centers on the interplay of evolutionary forces: mutation introduces new variation; natural selection alters frequencies according to fitness; genetic drift causes random fluctuations; gene flow (migration) mixes genetic material between populations; and demographic processes such as bottlenecks and expansions influence genetic diversity.

Core models and tools include the Wright-Fisher and Moran models, coalescent theory, and neutral theory. Researchers measure population structure with statistics such as F-statistics (Fst), heterozygosity, and nucleotide diversity, and infer history with allele-frequency spectra and haplotype data. Methods include maximum likelihood, Bayesian inference, and approximate Bayesian computation, as well as computational tools for ancestry inference like PCA, STRUCTURE/ADMIXTURE, and linkage disequilibrium analysis.

Data sources include genome sequencing, SNP arrays, and ancient DNA. Applications span human evolution and medical genetics, disease association and pharmacogenomics, conservation genetics, forensics, and plant and animal breeding. The field is highly interdisciplinary, combining biology, mathematics, statistics, and computer science to understand how genetic variation is generated and maintained.