Gene Flow (also known as gene migration), is any movement of genetic material from one population to another (The University of California Museum of Paleontology, n.d.).

 

The loss or gain of a certain type of allele can easily change gene pool frequencies even when there are no other evolution mechanisms operating. For example, if all red squirrels left the UK, the next generation there would be unlikely to have the red allele. Therefore the squirrel population in the UK would have  evolved and so too would the population into which the red squirrels had migrated to.

​

Gene flow can also occur without permanent migration. When organisms mate, a transfer of genes occurs between the populations even though both organisms return home. The new alleles are then spread through both populations.  

​

Finally, gene flow may also occur between different species. Segments of DNA may be transferred through vectors such as viruses as they invade the cells of plants and animals. This form of gene flow is uncommon and has only been documented in some species of insects, fish, reptiles, microorganisms and mammals. It is proven that 5% of the human and mouse genome sequences have been transported from other species by viruses (Magiorkinis G, 2015).