Factors impacting genetic diversity

​​In a nutshell

Gene diversity refers to the total number of alleles present in the gene pool of a species. There are multiple factors that can increase and reduce gene diversity.

Genetic diversity

​​Definition

Genetic diversity refers to the number of alleles present in the gene pool of a particular species. 

The greater variety of alleles present indicates greater genetic diversity for the species. Natural selection and genetic diversity go hand in hand to allow more advantageous alleles to be passed on to the offspring.

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Factors increasing genetic diversity

Gene flow

Gene flow refers to the transfer of alleles between two populations by interbreeding. ​This is a factor that increases genetic diversity. Gene flow most commonly occurs when two different species populations meet due to migration or other ecological factors. More mobile species like animals and humans have much higher rates of gene flow compared to species like plants.

Mutations

A mutation is an alteration or change in DNA caused by either mutagenic agents or epigenetic factors. Mutations are permanent and can be passed down to the offspring. Not all genetic mutations have a harmful impact; some may be beneficial to the phenotype of an organism. 

Factors reducing genetic diversity

Genetic bottleneck

Occurs when a large majority of organisms within a species population die. This reduces the total number of different alleles present in the gene pool of a species. Since the newer population will reproduce from a smaller number of individuals, their offspring will have a fewer variety of alleles to pass down as well.

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Example

An example of the genetic bottleneck effect is shown in northern elephant seals. The number of these species was significantly reduced due to hunting by humans. Since then, a population increase has been documented from $$50$$ individuals to a $$170,000$$​ seals. The offspring of these $$50$$​ northern elephant seals show a reduced genetic diversity.

The founder effect

This is a type of genetic bottleneck. This occurs when a few members of a large population start their own colony due to migration, geographical separation or even religion. Within the newer colonies, the frequency of alleles presented and expressed would be different compared to the original population. This would mean that a rarer allele can potentially be expressed much more commonly when compared to the original population. This reduces genetic diversity and increases the risk of genetic diseases.

Example

The Amish is a population in North America who have descended from a small number of Swiss individuals. These individuals have separated themselves from their surrounding populations due to religious or social beliefs. As a result, a fewer variety of alleles have been introduced into their gene pool. There is a higher risk of some specific genetic disorders because of the lack of genetic diversity.