Genetic Drift

Genetic drift is the change or fluctuations that occur in gene variants in a particular population (Jacquez, 2015). Genetic drift occurs when variant genes known as alleles change in number, either decreasing or increasing over time by chance. Genetic drift occurs in two types: the bottle neck effect and the founder effect.

The bottle neck effect is observed when a large percentage of a particular population is decimated mostly through a natural disaster such as floods or fire. The natural disaster only leaves a few of the species to reproduce. The population left is not representative of the previous genetic makeup of the original population. A bottle neck effect can be seen when natural disasters decimate a large part of the population (Jacquez, 2015). For example, a fire outbreak in a forest may kill over 95 percent of beetles and leave the rest which begin to reproduce. The 5 percent of the beetles left could be having a different genetic makeup from the vast majority of the earlier population. The new population would thus be different from the original population in terms of genetic makeup.

The founder effect as a method of genetic drift occurs when a small part of a population move away and inhabit a new area. This can lead to development of a new population that is quite different from the source population. The founder effect presents itself in a particular population due to reduced genetic variation. The new population lacks much of genetic diversity that was present in the source population (Jacquez, 2015). A good example can be seen in human populations where prevalence of particular diseases such as Huntingnton’s disease occurs frequently in the area around Lake Maraciabo, Venezuela. The high prevalence of the disease is attributed to a small group of individuals who chose to remain in the area. Some of the people had Huntington’s disease, which became dominant as the population grew.


Jacquez, J. A. (2015). CliffsNotes STAAR EOC Algebra I quick review. Boston: Houghton Mifflin Harcourt.