What is Gene Low? 

Gene flow, also known as gene migration, is the introduction of genetic material from a particular population to another population of the same species through interbreeding. For example, a bee facilitates its reproductive process by carrying pollen from one flower to another. The flow alters the composition of the gene pool of the receiving population. It introduces new alleles within the population and helps increase variability. This exchange of genetic material occurs through reproduction and brings about new combinations of traits into the population. Where human beings are concerned, actual migration of populations, whether voluntary or forced, brings about gene flow.  

Path of Gene Flow

Path of gene flow 

Consider two different populations from the same species, one originating in Germany and one in Mexico. The Amish person has her roots in Germany but now resides in Pennsylvania. The other population originates in Mexico and is a mix of Spanish natives and colonists. If the person from Mexico moves to Pennsylvania and marries the Amish girl, the offspring will have mixed genes of both parties. This example illustrates how gene flows from one region to another region of the world. 

Gene Migration 

Gene flow is the transfer of alleles, also known as gametes, from a particular population to a different population. This process is called gene migration. The flow causes the allele frequency of the population to change. So, when individuals belonging to a population migrate to another population, there are changes to the proportion of individuals who carry the same allele.  

Gene flow does not alter the allele frequency of a species as a whole but it changes the allele frequencies in a local population. The greater the difference in the allele frequencies between the migrant and the resident individuals and the larger the number of migrants during migration, the greater is the effect that the migrants will have on the genetic constitution of the receiving population. The addition to or loss of individuals from a population of species can change the frequencies of a gene pool despite a lack of operation of any other evolutionary mechanism.  

When physical barriers block gene flow, it results in allopatric speciation. This kind of geographical isolation stops the exchange of genetic material within populations of the same species. These physical barriers are usually natural. 

Gene Flow: Mechanism of Evolution 

Example 1 

When animals migrate to another population, they carry new alleles from the previous population to the new one. However, for the gene flow to happen, they must interbreed in the new population. As shown in the diagram below, a brown beetle is seen migrating to a population of green beetles. If the brown beetle can interbreed with a green beetle, there is a possibility of the brown exoskeleton to be passed on in the offspring’s DNA (deoxyribonucleic acid) structure. 

If two populations have a high gene flow, then they can be considered as one population as they share the same allele frequency. 

Example 2 

One of the best examples of artificial selection can be seen in dogs. Artificial selection helps establish traits through selective breeding. All dogs were wolves some 15,000 years ago. Some of these wolves or pre-dogs gravitated towards the new human settlements to scavenge, while the wolves moved away from civilization. Eventually, humans and dogs got dependent on each other. What is interesting is how different human populations used the dogs differently, and hence the new traits started developing. The sheepdogs and the hunting dogs were bred with fierce big dogs. Dachshunds were developed as barn dogs to hunt rodents. The breeders identified the desired traits and that’s how distinct dog breeds came into being. It is visible in the breeds like Puggle (half Beagle-half Pug) or Chiweenie (half Chihuahua-half Dachshund). When a dog from one population breeds with a pure breeding population, new alleles are introduced to the mix. The pool expands and new variations come into play. 

Allele frequency 

Alleles are the variant forms of a gene located in the same genetic locus on a strand of the chromosome. Allele frequency represents the appearance of a particular gene variant in a population. It can be represented as a percentage, a decimal, or a fraction. Allele frequency denotes the genetic diversity of a population. Any changes in the allele frequency indicate the genetic drift occurring in the population.  

Allele frequency can be defined as: 

$Frequency\text{ of allele A = }\frac{Number\text{ of copies of allele A in a population}}{Total\text{ number of A/a gene copies in the population}}$

When there are more than two alleles in a population, like A, a, and Ai, then adding up all the alleles will provide the denominator.  

Example 

A population’s gene pool can change through evolution over some time. Mechanisms like mutations, genetic drift, and natural selection come into play to alter the fabric of the gene pool. Finally, the pool adapts to the needs of the environment the population thrives in.  

When populations migrate from equatorial regions towards the cold of the northern regions, people had paler skins due to relatively low exposure to sunlight. This change in skin pigmentation hence becomes a part of the evolved gene pool of the population. The larger the size of the gene pool, the more is the ability of the population to adapt and change. Narrower gene pools do not handle dynamic environmental changes successfully.

Summarization for Gene Flow Quiz-Let  

Gene pool: It can be defined as the combined genetic diversity contained inside a species or a population. Any big gene pool with extensive genetic diversity will be able to better handle and endure the environmental challenges posed to a population.  

Interbreeding: Inbreeding refers to the mating of organisms closely related through similar ancestry. It leads to the creation of a small gene pool which can result in extinction when faced with environmental challenges. Inbreeding can help retain desirable characteristics but is unable to handle the stress of environmental changes due to the combined effect of harmful recessive genes from both parents.  

Natural selection: Charles Darwin, an English Naturalist, developed the concept of natural selection. It is a process of adapting and changing by a population of living organisms. Each individual is naturally variable in a population. Individuals with adaptive traits have a better chance of surviving and reproducing. These adaptive traits then get passed on to the offspring. Natural selection helps transmit favorable traits through generations. 

Mutations: Mutations refer to the changes in the molecular structure of genes called DNA. It is an important source of bringing about genetic variations in a population. Mutations can be accidental or can happen due to exposure to some harmful radiation or chemicals in the environment. 

Genetic Variation: The diversity found in gene frequencies is referred to as genetic variation. These variations can be the differences among individuals or populations. Mutations, sexual reproduction, and genetic drift are the sources of genetic variation. 

Common Mistakes

There is a common misconception where genetic drift is confused with other evolutionary mechanisms or evolution itself. At times genetic drift is confused with random mutation. Another big misconception regarding genetic drift is that it is often confused with gene flow.  

Genetic drift refers to the process of evolution, where the allele frequency of a population changes due to chance or natural sampling errors (natural disasters like earthquakes and floods) over time. The effects of genetic drift are strongly visible in smaller populations. 

Gene flow, also known as migration or allele flow occurs when genetic material is transferred from one population to another. In cases with a high rate of flow, two different populations end up with equivalent allele frequency and can be effectively considered as one single population. 

Context and Applications 

This topic is significant in the professional exams for both undergraduate and graduate courses  

• Bachelors in Genetics 
• Bachelors in Evolutionary Biology 
• Bachelors /Masters in Anthropology 
• Masters in Biotechnology 
• Master of Science in Genetic Engineering  

Related Concepts 

1. Anthropology 
2. Industrial biotechnology 
3. Genetically modified organism (GMO) 
4. Evolutionary biology