🧬 Genetic Drift

Population size N 50 Initial frequency p₀ 0.50 Replicate populations 12 Generations 200 Weak selection (s = +0.02 for A) Mutation (μ = 0.001, a↔A)

Presets

Small N (fast drift)

Large N (stable)

50/50 start

Weak selection

Generation0

Fixed (p=1)0%

Lost (p=0)0%

Segregating100%

Mean heterozygosity—

Mean time to fix/loss—

Effective N (Ne)—

In the Wright-Fisher model each generation draws N diploid individuals (2N alleles) by binomial sampling from the parent allele pool. With no selection the expected frequency is unchanged, but sampling variance makes p wander until it fixes (p=1) or is lost (p=0). Smaller populations drift faster; heterozygosity 2p(1−p) decays by a factor (1−1/2N) each generation.