Simulation of Mutation plus Drift
Mutations in a PopulationMutations are the ultimate source of all genetic variation.
Mutations produce new versions of genes (new alleles). When new alleles appear, the genetic variation in a population increases.
mutations new alleles more genetic variation
How often do mutations occur? The mutation rate
The mutation rate is the number of mutations per genetic unit (gene, base, or product) per unit time (year, million years, or generation). This is how to calculate the mutation rate:
Consider the worm population below. The population size (N) is 3. Each worm has a complete gene sequence that is 10 bases long. Only new mutations are flagged with an M.
What is the mutation rate per gene per generation? What is the rate per base per generation? How many mutations can you expect an average worm to carry?
Here are some mutation rates for your favorite organisms.
Notice that mutations are very rare. Mutation rates are very low for most organisms. Think about it, you might look at three million gametes and only find ten mutants.
On the other hand, mutation happens. [calculations still needed here] insert
Mutation Drift Balance
In the Genetic Drift Simulation, the number of color alleles in the population (genetic variation) decreased due to genetic drift (eventually to only one allele).
The University of Arizona
April 27, 1999
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