Simulate how random genetic drift changes allele frequencies over generations in finite populations, visualizing evolution and population genetics principles.
Final Allele Frequency
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Total Frequency Change
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Fixation Events
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Loss Events
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Genetic drift is the random change in allele frequencies in a population over time due to sampling effects during reproduction. It's more pronounced in smaller populations and can lead to the loss or fixation of alleles regardless of their selective advantage.
Smaller populations experience stronger genetic drift because random sampling has a larger proportional effect. In large populations, random changes tend to cancel out, while in small populations, chance events can dramatically alter allele frequencies.
Allele fixation occurs when an allele reaches a frequency of 1.0 (100%) in the population, meaning all individuals carry that allele. Once fixed, the allele cannot be lost except through mutation or migration.
Mutation introduces new genetic variation and can counteract the loss of alleles due to drift. Higher mutation rates maintain more genetic diversity, while lower rates allow drift to more easily fix or eliminate alleles.
Each simulation represents one possible evolutionary pathway under random genetic drift. The stochastic nature of drift means that identical starting conditions can lead to very different outcomes, demonstrating the unpredictable nature of evolution in finite populations.
In neutral evolution (no selection), the probability that an allele will become fixed equals its starting frequency. An allele starting at 0.3 frequency has a 30% chance of fixation, while one at 0.7 has a 70% chance.
Look at the trajectory of allele frequency over time and note whether it trends toward 0 (loss) or 1 (fixation). The variability between simulations shows the random nature of drift, while the overall patterns reveal underlying population genetic principles.