The results of one model used to describe this phenomenon can be obtained by solving the Markov chain associated with the model, named for Wright and Fisher. In the Moran model this phenomenon occurs twice as quickly as in the Wright-Fisher model due to a tridiagonal transition matrix. In Kimura's neutral theory, this phenomenon, rather than natural selection, drives evolution. Random environmental events cause the bottleneck effect, a type of this phenomenon, and small initial groups experience this phenomenon's founder effect. For 10 points, 
The results of one model used to describe this phenomenon can be obtained by solving the Markov chain associated with the model, named for Wright and Fisher. In the Moran model this phenomenon occurs twice as quickly as in the Wright-Fisher model due to a tridiagonal transition matrix. In Kimura's neutral theory, this phenomenon, rather than natural selection, drives evolution. Random environmental events cause the bottleneck effect, a type of this phenomenon, and small initial groups experience this phenomenon's founder effect. For 10 points, name this phenomenon that is the random change in allele frequency in a population.
The results of one model used to describe this phenomenon can be obtained by solving the Markov chain associated with the model, named for Wright and Fisher.