This graph shows ten different populations, each consisting of two individuals.

Initially, each population has p = 0.5 and q = 0.5

Each population might take a different time to become "fixed" at one allele or the other, but all of them eventually do.

For example, due to sampling error, two of the populations become fixed at "a" in only one generation. Two more take two generations.

Note that the "4" on the diagram is the total number of alleles in the population, since each individual has two.

The populations that eventually go to "0" frequency for the a allele have become fixed for the "A" allele.