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