Migration — Role in Allele Frequency & Natural Selection

Migration, Alleles, and Gene Flow

Genetic migration can either introduce new alleles or remove alleles from a population. Genetic migration is sometimes called gene flow. You may know "migration" as when birds or other organisms move to a different location for part of the year. In population genetics, migration for genes is a bit different.

• Immigration: If some organisms join a population, they might bring new alleles into the gene pool. In other words, they add genetic diversity. During immigration, the organisms move into a different, existing population.

• Emigration: If some organisms leave a population, they may take some alleles away from the gene pool. This reduces the genetic diversity of the original population. During emigration, the organisms exit their population.

Basically, any organisms moving into or out of a population can change the gene pool. This has a direct effect on genetic diversity.

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$\color{#8925AE}{\text{Migration}}$ : The permanent movement of genes into or out of a population, causing a change in allele frequency

Entering or Leaving a Population

Migration can either increase or decrease genetic diversity. As individuals leave or enter a population, they bring or take away unique alleles.

• Immigration is the movement of individuals into a population. It increases genetic diversity.

• Emigration is the movement of individuals out of a population. It decreases genetic diversity.

Remember that alleles are different versions of a gene. By having many versions of a gene, a population remains healthy. Immigration and emigration allow for gene flow between different populations. A steady migration rate allows all of the populations of a species to remain healthy and have a high amount of genetic diversity.

Remember, this is a bit different than natural selection because the genes that are entering or leaving a population are random.

Migration and Gene Flow

One way species combat genetic drift is through the migration of alleles. This is called gene flow. Gene flow is when alleles either enter or exit a population. Entering is called immigration, and exiting is called emigration.

When new, genetically unique individuals immigrate to a preexisting population, they bring along new alleles with them. When the new organisms mate with the preexisting ones, this enhances the species' overall genetic variation by creating new combinations of alleles.

Emigration happens when genetically unique organisms leave one population for another. It is another form of gene flow, but it usually results in decreased genetic diversity. This is because rare alleles leave the existing gene pool.

(Video) Gene Flow - Migration

by Brightstorm

This video defines immigration and emigration. It also makes sure you know the difference between migration and gene transfer.