Summary

There are four characteristics of genetic drift that I think are particularly important for you to remember:

1. Allele frequencies tend to change from one generation to the next simply as a result of sampling error. We can specify a probability distribution for the allele frequency in the next generation, but we cannot predict the actual frequency with certainty.

2. There is no systematic bias to changes in allele frequency. The allele frequency is as likely to increase from one generation to the next as it is to decrease.

3. If the process is allowed to continue long enough without input of new genetic material through migration or mutation, the population will eventually become fixed for only one of the alleles originally present.¹³

4. The time to fixation on a single allele is directly proportional to population size, and the amount of uncertainty associated with allele frequencies from one generation to the next is inversely related to population size.