Wright-Fisher Genetic Drift

Population N: 100 Initial freq p₀: 0.50 Selection s: 0.00 Mutation μ: 0.000 Trajectories: 20

N: —

p₀: —

Fix. prob (theory): —

Fix. prob (sim): —

Fix. time ~2N ln(N): —

Lost: —

Fixed: —

Active: —

Wright-Fisher sampling:

p_{t+1} ~ Binomial(2N, p*)/2N

p* with selection s:

p* = p(1+s)/(1+sp)

Drift alone — fixation prob:

Π(p₀) = p₀

With selection:

Π = (1−e^{-2Nsp₀})/(1−e^{-2Ns})

Mean fix. time (neutral):

T_fix ≈ −4N(p₀ ln p₀ + (1−p₀)ln(1−p₀))

Wright-Fisher Model