Gene Flow Definition, Examples, and How does It Prevent Speciation – The male lion leaves the group where it was born, and heads to a new group for mating. This leads to the flow of genes between groups of lions.
Gene flow is an exchange of genes between populations, which is usually the same species. Examples of gene flow in a species include the migration and breeding of organisms or the exchange of pollen. Gene transfer between species includes the formation of hybrid organisms and horizontal gene transfer.
Migration in or out of the population can change the frequency of allele, as well as increase genetic variation into a population. Immigration can add new genetics to existing genes in a population. On the contrary, emigration can eliminate genetic material. Because reproductive separation between two gene-based populations is necessary for speciation to occur, gene flow can slow this process by spreading different genetics between populations.
Gene flow is blocked by rows of mountains, oceans, and deserts. Even human buildings like the Great Wall of China can block the flow of plant genes.
Gene Flow Definition
To understand the definition of gene flow well, we must start with the definition of genetic population. In genetics, a population is defined as a group of organisms of the same species, capable of reproducing with each other and sharing the same habitat.
To give you an idea, humans from different cities can be considered individuals from different genetic populations because they come from the same species (humans) and share the same habitat (cities, such as New York or LA).
Individuals in a population have a certain frequency of alleles (a certain proportion of gene allele), which can change over time if any or all of the situations described by Hardy-Weinberg’s law occur: gene selection, mutation, drift, and flow.
Gene flow is nothing more than the flow or transfer of allele frequencies from one population to another or between two or more populations reciprocally. Usually this allele flow occurs because a population moves to another person’s “territory” or habitat and reproduces with the individuals living there.
In this case we can distinguish two populations: the donor population (which donates alleles, that is, that includes them into the population that lives there) and the recipient population (which receives alleles that have been introduced by new populations that have traveled to their habitat).
Imagine that the population of ten men in NY will live in LA, where they reproduce with ten LA women: in this case the donor population is ten NY men and the recipient population is LA. If some of the couple’s children return to NY, the recipient population will also be the recipients and will become gene streams in both directions.
Usually, population genetics relate to animal populations because the population must consist of individuals of parents belonging to the same population, which is incorrect in the human population and, although rare in natural animal populations, it can occur.
Gene Flow Example
In recent years, gene flow has been observed between the Caucasian population and the African-American population. African-Americans are descended from native West Africans, while Caucasians are descended from native Europeans.
The African-American population is inherently resistant to malaria whereas, the European population is not. The offspring produced by mating of individuals of this population looks resistant to disease.
Another example of the gene flow was during the Vietnam War, when American soldiers mated successfully with Vietnamese women, in the 1960s and 1970s, and changed the frequency of allele from the Vietnamese population.
A grain of pollen from wind-pollinate plants successfully fertilize several other plants to produce seeds that give rise to viable offspring, then changes in the frequency of alleles can be carried.
How does gene flow prevent speciation?
Speciation is an evolutionary process that can lead to the formation of new species. This is basically the separation of lineages. Genetic variation due to mutation accumulation and natural selection of individuals with this variation is necessary for speciation to take place.
Sustained gene flow between two populations can lead to aggregation of two gene pools. It uniforms the frequency of genes by reducing the genetic variation of the two populations. This leads to negating the genetic differences necessary for speciation to take place. It can therefore be said that gene flow has a negative effect on speciation.
- Image: Jessica Krueger, CC BY-SA 3.0 https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons
- Video: Susan Bibbs