Labs / Biology
Genetic Drift
Each colored line is one isolated population passing an allele down the generations by random sampling — no selection, no migration, just luck. Shrink the populations and watch how quickly chance alone pushes some to fixation and others to loss, dragging the average heterozygosity (the dashed line) toward zero.
gen 0fixed 0/12lost 0/12H̄ 0.500
What to try
- Drop the population size to 5. How many generations pass before most lines slam into fixation or loss?
- Crank the population size up to 400. Why do the lines suddenly stay huddled near the middle?
- Start at frequency 0.1 — are populations more likely to fix the allele or lose it, and why?
- With 24 parallel populations at 0.5, roughly what fraction end up fixed versus lost once they all settle?
- Watch the dashed mean-heterozygosity line: does small versus large population size change how fast diversity drains away?