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Genetic Drift and Founder Effect

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Catastrophic Events

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Genetic Drift

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Founder Effect

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Genetic Drift

evol-treeGenetic drift refers to changes in the frequency of alleles within a populace. Genetic drift impact is greater in smaller populations, as there is a smaller gene pool for the changes to dilute. On the off chance that the impacts of genetic drifts are particularly pronounced, the allele may be totally expelled from the populace, lessening the measure of variety in the population's gene pool.

Types of Genetic Drift

  • Population Bottleneck

Population bottleneck occurs when a large population is drastically reduced rapidly. When this happens, alleles can be eradicated entirely from the population if all of the organisms with them die off.

An example of this type of genetic drift can be seen in what occurred with the northern elephant seal. Across the board, their genetic variations have been greatly reduced due to being killed or hunted. There were as few as 20 individuals at one time! Although their population has since bounced back to more than 30,000, signs of their bottleneck can be seen.

  • Founder Effect

This effect results from one group of organisms from one population moving on and colonizing another area independent from the original populace. When this happens, it not only rapidly decreases the population, but perhaps more importantly, affects the genetic changeability of the original population.

An example of the Founder Effect can be seen if one takes a look at the Afrikaner population of South Africa. They originated from a very small group of Dutch pilgrims. Today, the Afrikaner population has uncommonly high rates of Huntington's disease. It is thought by many that it was the Dutch pioneers arriving in South Africa that uniquely carried this particular trait. Coincidentally, they carried that quality with strangely high recurrence. Although not considered by most scientists to fall into the category of a hereditary sickness, it is thought that this and many other traits unique to this population were particularly a result of the intermixing of people with traits at high frequencies.

Genetic Drift Factors

  • Mating Patterns

When one within a population mates with another of the same population, it can cause many undesirable attributes. The offspring that result from this mating can have higher instances of certain negative traits as a result of this hereditary mix.

  • Distribution

The actual physical dissemination of organisms can impact a population as well. To this end, creatures that form part of different categories of animals that experience expansive conveyance might occasionally also display similar hereditary cosmetics traits across the entire species. 


Migration, also known as relocation,  refers to the movement of organisms from one place on the next.  

The impact of this process on allele frequencies is profound. When the migrant mates with those at its ultimate destination, it contributes its gametes, and therefore alleles, to the genetic mix. It’s through that process that the corresponding alleles will adjust to the already populous alleles within the receptor.


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