Gene Flow

We know that genetic variation is an essential component of the evolutionary process as it facilitates natural selection. Gene variations refer to the differences of genetic makeup in organisms of a population. Several sources play a significant role to give rise to variations of genes in a group. Gene flow is one such source. 

What is Gene Flow? 

It is a phenomenon where new genetic traits are introduced in a population due to interbreeding with another group. It is also called migration because of the constant flow of individuals in or out of a population which affects the composition of the gene pool of a receiving population. 

Generally, if the number of migrants is large and there is a considerable difference in gene frequency between the migrants and residents, then the former will have more effect in changing the genetic composition of the latter.

However, if two groups constantly interbreed within themselves, they will also start sharing a common gene pool which reduces genetic variations.

Factors Influencing Gene Flow

Several factors that are responsible for the flow of genes in and out of a population. These are discussed in detail below - 

• Mobility

According to gene flow definition, when individuals from one population breed with members of another population, they introduce new allele traits which change the genetic structure of the second group. Most animals and human beings, on reaching maturity, leave their herd or family to mate with members of other groups. For instance, if green parrots are introduced to a population of red jungle parrots, it will lead to more variations of colour in the jungle parrot’s gene pool. 

Another gene flow example can be when individuals from Africa where malaria is rampant, mate with Europeans. The offspring will carry the antibodies of malaria inherited from his/her African parent. 

Pollen grains are transported from one plant to another for pollination by birds, wind, insects like bees, etc. 

Nonetheless, an organism with greater mobility has more chances of migration which is why more genetic variations can be seen in animals than in plants.

• Environmental Factors

In some cases, environmental factors may also lead to variations of a gene in a population. For example, let us consider a group of birds living on the mainland by the sea. Due to a natural disaster such as a storm or earthquake, some birds might get separated from the larger group and end up on an island in the middle of the sea. 

If the island has very little vegetation, the birds which were previously used to eating food grains will have to adapt to hunting and eating insects.  Thus, over time, along with their physical appearances, the genetic makeup between two groups of birds will also become different. 

Factors that Prevent Gene Flow

Some restrictions that prevent gene flow between populations are as follows – 

Geographical Barriers - Sometimes, geographic barriers such as continental drift, deserts, vast oceans, and high mountains prevent migration in and out of a population. If the population is isolated for a long time, then its genes may diverge significantly from other related groups.

In such situations, if the members of the isolated group are not able to reproduce with any other community, they will be considered an altogether separate species. 

Apart from that, human activities such as cutting down forests, building dams also lead to geographical isolation between species.

Reproductive Barriers - Aside from the external restrictions as discussed above, there are also internal barriers in the form of reproductive organs that prevent the gene flow between species. Several species have evolved to form different reproductive organs, which prevent them from mating with each other. 

In addition to that, various species have different mating seasons and mating rituals or calls which has resulted in reproductive isolation. 

You can go through detailed articles on genetics, and other related topics on our website to know more about gene flow meaning. The articles cover each topic in detail along with diagrams and charts which will aid you to understand the underlying concepts better. 

You can also download these study guides on gene flow in pdf format through our mobile platform to prepare for your examinations at your own pace.  You can download our Vedantu app for enhanced access to these study materials and online interactive sessions for better clarity.