Gene Flow and Factors Affecting: Definition, Types, Examples, Process

What is Gene Flow?

The gene flow or gene migration is the process by which genetic material is exchanged between different populations, either by the bodily movement of individuals or by the transport of gametes. This process takes place when two organisms from two different populations mate, and as a result, the alleles of one population intermingle with another population.

Thus, gene flow is deemed important in evolutionary biology as it brings in a fresh stock of genetic differences within a population. Hence, enabling them to adapt to changing environments as well as check cases of genetic differentiation that may give rise to speciation. Thus, gene flow contributes to the preservation of genetic continuity and differentiation, which accordingly affects the processes of species evolution.

Mechanisms of Gene Flow

The mechanism of gene flow includes migration, dispersal of genes, and the kind of mating systems. The mechanisms are described below-

Migration

• Migration is the act of change of individuals from one population to another and consequent breeding. Usually, it is described in terms of small distances and large distances and is regarded as one of the most effective delivery channels for genes.

• In animals, migratory creatures, for instance, birds and fish, change their routes with ease due to the ease of gene flow. For instance, salmon go to seawater and perform reproduction, then go back to freshwater and interbreed, fusing genes between different populations. In plants, species like trees can also displacement slowly through a progression of seed dispersion; though again it is not as frequent as in animals.

Dispersal

• Seed/Spore dispersal is a process in which seeds/spores are separated from the parent plant. This may be through wind, water, or even an animal, which enables it to colonise a new area and also interbreed with a population in a different area.

• Dispersal also applies to animals, where these move around in search of other areas or resources to feed on.

• For instance, insects might pass through the air to new/ other locations while the organisms of the Mammalia class could pass their genes through the territory of the new areas or migration.

Mating Systems

• Random breeding happens when people mate randomly, that is, without regard to their genetic make-up and therefore encourages gene mobility and gene interchange.

• This means that factors that affect the pairing patterns of reproduction can favour certain genes within values and against other values. In the human conception, this can occur through incest or where individuals choose their partners based on some genetic make-up.

• For example, many wild populations are considered to mate randomly, which means the selection of a mate is done randomly. However, in some species, it is observed that there is a preference for those of similar type to be paired, thus influencing the genetic system and possibly resulting in localised adaptation.

• Knowledge of these mating systems is important while dealing with phenomena of the genetic structure and evolutionary processes.

Factors Affecting Gene Flow

Gene flow is affected by the following factors such as geographical barriers, behavioural barriers, ecological barriers, and anthropogenic barriers. The factors are described below-

Geographical Barriers

• Physical barriers such as mountain ranges, rivers, and seas may also slow down or prevent the transport of individuals from one population to another, thus restricting gene flow.

• These physical barriers are capable of severing the interactions among different groups of people, which cause genetic differentiation.

• For example, the finches of the Galápagos are different on different Islands because the effect of geographic isolation is different.

• Also, the same process of construction of the Isthmus of Panama introduced a geographical break that restricted the mobility of different marine animals and thus encouraged speciation for the oceans of the Atlantic and Pacific.

Behavioural Barriers

• Some of these include the ability to limit the chances of gene flow because certain behaviours of preference will influence the kind of individuals that are likely to breed.

• This means that over time reproductive isolation and divergence may be experienced due to the limitations in mobility of some plants and animals.

• This is particularly important because, in many bird species, males could have some courtship characteristics that are not recognizable by females from another population; therefore, leading to no reproduction.

• Likewise in the case of frogs, the variation in some of the characteristics such as mating calls can result in reproductive isolation.

Ecological Barriers

• Dispersal ability can be restricted if species have specific habitat needs or ecological traits in which they are found, thereby preventing individuals from the population not coming into contact.

• It would affect gene flow between populations adapted to different soils or climates, for instance, plants that require specific soil or climate conditions to germinate and grow may carry seeds to areas that cannot support their germination and growth.

Anthropogenic Barriers

• Some human activities, such as the construction of cities and deforestation, make it difficult for the animals to interbreed since they offer hindrances such as physical barriers, such as walls, roads and water systems.

• They can also find themselves in a state of subdivision, and, as a result, cannot mix with other groups of the same kind, which may be a result of urbanisation.

• For example, the construction of roads and urban development isolates populations, leading to a decrease in the amount of genetic variation and a consequent increase in inbreeding.

Consequences of Gene Flow

Gene flow leads to a variety of consequences, ranging from genetic diversity, population adaptation and speciation. Those consequences are described below-

Genetic Diversity

• It is important for the well-being and existence of populations since it ensures easier adaptation to environmental conditions or diseases.

• This, on its part, implies that high genetic diversity gives a wide array of traits, thus increasing the durability and sustainability of species.

• This is an important process and it aids in the proliferation of genetic variation by adding fresh alleles, which are central in diminishing variations together with chances of breeding.

• This process assists populations in retaining the ability to be adaptable or transform over a period.

Population Adaptation

• Gene flow helps in adaptation because it moves the beneficial alleles from one population to another.

• Thus, when people from different stocks get together and start breeding, valuable genetic mutations or superior traits may be passed on, which helps to maintain desirable fluctuations in the population.

• For example, using gene flow, hindered by the isolation of gene pools which define certain populations of plants or animals.

• Genes which can provide resistance to extreme temperatures caused by climate change or other adverse environmental conditions will be promoted among populations that harbour genetically diverse organisms.

• The movement of some bird species from one area to another is useful given changes in weather conditions across their different zones.

Speciation

• Speciation is known to be retarded in this manner by processes such as gene flow in as much as they keep the populations genetically connected.

• However, speciation arises when gene flow decreases because of either geographical or behavioural isolation, which in turn causes various populations to develop their distinct genetic variations owing to genetic drift.

• Examples: For instance, cichlid fish in the African Great Lakes, where populations are rather divided, and gene exchange is minimal, give rise to a great number of species.

• On the other hand, we have that kind of gene flow that persists within the different populations and can slow down or even stop the process of the formation of new species.

Recommended video for "Gene Flow"

MCQs on Mechanism of Evolution: Gene Mutation & Gene Flow

Q1. Assertion: Gene mutations contribute to variations within the gene pool of a population.

Reason: Gene mutations introduce new genetic variations into the gene pool, contributing to increased diversity and variations within the population.

Option 1: Both the assertion and the reason are true, and the reason is a correct explanation of the assertion.

Option 2: Both the assertion and the reason are true, but the reason is not a correct explanation of the assertion.

Option 3: The assertion is true, but the reason is false.

Option 4: The assertion is false, but the reason is true.

Correct answer: (1) Both the assertion and the reason are true, and the reason is a correct explanation of the assertion.

Explanation:

The assertion states that gene mutations contribute to variations within the gene pool, which is supported by the given text. The reason correctly explains this by stating that gene mutations introduce new genetic variations into the gene pool, leading to increased diversity and variations within the population. Therefore, both the assertion and the reason are true, and the reason effectively explains the assertion.

Hence, the correct answer is Option (1) Both the assertion and the reason are true, and the reason is a correct explanation of the assertion.

Q2. A spontaneous mutation results in a couple having only female progeny. When the daughter marries and has children, none of them are males. However, in the third generation, there are few male offspring. What is the most likely explanation of this observation?

Option 1: The mutation reverses spontaneously in the third generation

Option 2: The mutation occurs on the X chromosome and is both recessive and lethal

Option 3: The mutation occurs on the X chromosome and is both recessive and dominant.

Option 4: The mutation occurs on an autosome and is dominant

Correct answer: (2) The mutation occurs on the X chromosome and is both recessive and lethal

Explanation:

This spontaneous mutation has occurred on the X chromosome and is both lethal and recessive. The Female is the carrier and thus survives while the male is unable to survive due to their hemizygous condition.

(female) Survives (Carrier)

(male) lethal allies)

Hence, the correct answer is Option (2) The mutation occurs on the X chromosome and is both recessive and lethal

Q3. If the migrating individuals interbreed with members of the local population, these may bring new alleles into the local gene pool of the host population termed as

Option 1: Organism migration

Option 2: Population migration

Option 3: Gene mutation

Option 4: Gene migration

Correct answer: 4) Gene migration

Explanation:

A process known as gene flow or migration occurs when migrant individuals interbreed with local population members, adding new alleles to the local gene pool. This genetic material exchange can affect allele frequencies and boost the host population's genetic diversity, which can impact evolutionary processes. Gene flow may reduce genetic differences between populations, preventing speciation, and transferring beneficial alleles that improve the population's adaption to its environment.

Hence, the correct answer is option 4) Gene migration

Also Read-

• Practice MCQs on Gene Mutation and Gene Flow

• Biological Evolution

• Theories of Evolution