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The Migration of Genes – Gene Flow
The travel of genes through and between populations across geographical barriers is called as ‘Gene flow’. Gene flow is identified as one of the tool to evolution. Evolution is the term applied to a population when a new variant is derived from a common population due to changes in genetic characteristics. This change in genetic characteristics a cause for evolution can be due to mutation, genetic drifting, Natural selection, Environmental fitness- survival of the fittest and Gene flow.

The Mechanism of Gene flow: A species or animal or individual detaches from its own group (population), migrates and enters the other group, brings a change in the characteristics of the native population by passing its gene through reproduction. This clearly indicates the change in genetic nature of a native population by the migrated individual is possible only through fusion of gametes, reproduction.

Types of Gene Flow: The observation of the travel of the gene between the source and the destination is useful in classifying gene flow into two types. They are intra species gene transfer and interspecies gene transfer. For example if the gene flow is between a goat of one population and a goat in the other population then it is called as intra species gene flow. Whereas if the gene flow is between a bacteria and a plant then it is called as the inter species gene transfer. The gene flow among the same species is also called as the vertical gene flow and the gene flow between different species is called as the horizontal gene flow.

Hurdles to Gene flow: The two main hurdle restricting gene flows are the motor skill of the migrant species and the geographical barriers. The motor skill of the migrant species decides the rate at which the species moves. Higher the movement, greater is the rate of gene flow. The geographical barriers restricting gene flow include natural barriers like mountains and oceans and anthropogenic (by man) barriers like reservoirs, constructions made by humans to form boundaries etc.

Humans and gene flow: The best example of gene flow in humans is cited by the mixed population of the US state. Research has proved the transfer of malaria resistant gene from the migrated population to the native population among whom the gene was absent originally. Humans are not bound to the restriction factors like physiological barriers in gene flow.

Micro organism and gene flow: The gene flow in microorganisms like viruses and bacteria can be either within the same species or between different species because of its ability to infect and multiply in the host cell. An evidence of transfer of gene from a soil bacterium to plants is identified.

Plants and gene flow: The common gene flow pattern in plants is through pollen grains which are carried from one place to plants present in another locality by wind or by insects. Both horizontal and vertical pattern of gene flow occurs in plants. The vertical pattern of gene flow is through hybridization which involves producing a new plant variety with desirable characteristics by crossing two different plants of the same species. Hybrid variety of hibiscus is a good example of vertical pattern of gene flow. Also horizontal gene flow is observed in plants where genes are transferred from bacteria to the plant naturally. Gene flow from a transgenic plant (plant carrying a foreign gene received through gene transfer technology) is a concern due to increased chances of flow of genes with novel characteristics to some other species of plant. Also if a plant is created with a desired characteristic of antibiotic resistance by inserting the desired gene, the chances are that, the gene may be transferred to bacteria infecting the plant and thus the bacteria will develop the characteristics of antibiotic resistance, posing danger to humans.

Gene flow is a natural phenomenon in the process of evolution involving transfer of genes from one population to the other crossing all geographical barriers. Whereas human induced gene transfer uses the technologies like rDNA technology, genetic engineering, molecular cloning which is done with an aim to create a new variant or species beneficial for the human kind. There is no evidence of danger or undesirable effects observed in the natural process of gene flow as it is well balanced and managed by the nature itself.
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Migration is the movement of populations, groups or individuals. In genetic terms, migration enables gene flow: the movement of genes from one population into another. If the two populations originally had different gene frequencies and if selection is not operating, migration (or, to be exact, gene flow) alone will rapidly cause the gene frequencies of the different populations to converge.

Migration will generally unify gene frequencies among populations rapidly in evolutionary time. In the absence of selection, migration is a strong force for equalizing the gene frequencies of subpopulations in a species. Provided that the migration rate is greater than zero, gene frequencies will eventually equalize. Even if there is only one successful migrant per generation, gene flow inevitably draws the population's gene frequency to the species' average. Gene flow thus acts to bind the species together.
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