Dhristi NEET 2022-24

What is Gene Pool?

Gene pool is the collection of different genes in a population of a particular species at a given time. The gene pool is used typically for referring to the population of individuals of a particular species and the gene pool definition includes all the genes and combinations of genes in the population. The gene pool term includes the sum of all the alleles of genes present at all of the loci within a population of a single species. Thus, the gene pool definition is the term used to describe the set of all the genes, or genetic information in any population that too of a particular species. 

 

Concept of Gene Pool

The concept of gene pool was formulated by the Russian geneticist Alexander Sergeevich Serebrovsky, who coined the term genofond, the English translation of which is the “gene pool”. A large pool of genetic diversity of a single species is known as the gene pool. This includes all the alleles present at a given loci in the population of a particular species. The gene pool meaning also includes all the genes independent of their expression i.e. whether they are expressed or not, they are all considered in the gene pool meaning. The gene pool is usually considered when the population is robust and can survive intensive natural selection processes. 

 

Another concept that is linked with the concept of gene pool is the concept of biological fitness. Biological fitness is determined by the capacity of a gene pool of a particular species to survive through various changes that can lead to intensive natural selection. The elimination of a species due to varying conditions in an ecosystem can occur if the species cannot withstand those changes. This ability of a species to withstand the changes is known as biological fitness. The biological fitness of the species can be determined by the gene pool. If the gene pool consists of a lot of diversity in the alleles then the biological fitness of the species is said to be high but if there is low diversity then the fitness of the species is said to be low. Thus, high genetic diversity in the gene pool as per the gene pool meaning leads to high fitness whereas low genetic diversity arising due to inbreeding or bottleneck events can cause reduced biological fitness and increased chances of extinction.

 

There are certain considerations in which even with low genetic diversity i.e. reduced biological fitness the species can survive if the fitness is increased by phenomena such as genetic drift. Genetic drift is the change in the frequency of a particular gene variant - the allele, for a particular species. If due to such changes, new genetic variants, more adaptable to the changing conditions,  are introduced in the population of the species then there are chances of increasing the biological fitness of the species even when the diversity in the gene pool is low. Thus, the gene pool meaning itself does not indicate biological fitness but is an indicator of biological diversity which gives relevant information regarding the fitness of the population of the species. 

 

Changes in the Gene Pool

The changes in the gene pool can cause changes in the genetic diversity of the population of the species as well. The composition of the gene pool can change over time through processes that govern evolution. A variety of mechanisms such as mutation, natural selection and genetic drift can cause changes in the composition of the gene pool. These changes are essential for the survival of any population of species with the changes in the environment. A diverse gene pool gets created through these genetic variations which make the individuals in the population adaptive to the changing environment. Such an example of change can be seen with the changes in the human gene pool as well. When the human population migrated from the equatorial regions towards the northern climates, there was a change over time in skin pigmentation. When the human population was exposed to relatively low sunlight the colour of the skin changed to a lighter colour for increasing Vitamin D absorption. The genetic modifications that occurred due to changes in the environment then became a part of the human gene pool in that particular region.

 

As mentioned earlier, the gene pool shows the diversity of the alleles present in the population which in turn is an indication of biological fitness. The ability of the population of a particular species to adapt to a particular environment and to evolve can be partly influenced by the gene pool. These changes can be useful in creating diversity in the said gene pool. But this does not mean that genetic diversity and gene pool in a sentence will mean the same thing. Genetic diversity in itself is a characteristic arising from various processes leading to the creation of a population of species. It can either have only a single genetic variation of a gene or multiple alleles in a population comprising a gene pool. Thus, it should be noted that each is a factor indicating another.

 

Types of Gene Pool in Crop Breeding

Harlen and wet defined three types of gene pools for the classification of each crop and its related species as compared to formal taxonomy. They are:

  • Primary Gene Pool: The members in this pool are of the same species and can inter-mate freely. The peculiarity of this gene pool is that crossing is easy, producing fertile hybrids with good chromosome pairing, and normal gene segregation causing easy gene transfer. 

  • Secondary Gene Pool: This gene pool consists of the species that are not the same but more closely related to a particular primary gene pool. The crossing can produce hybrids but they may be infertile i.e. less fertility, and the chromosome pairing and gene segregation can also be bad. Yet it still offers significant potential to produce any type of hybrids.

  • Tertiary Gene Pool: This pool consists of totally different species from the gene pool in consideration and there is very little or almost nil possibility of producing any hybrids by crossing. It can be said that this is the shallow end of the gene pool.

 

Thus, from the given article the definition of the gene pool and its various characteristics are understandable including the different types of the gene pool. 


Gene Pool Centers

Gene pool centers are places in the world where significant crop plants and domestic animals first appeared. They have an incredible variety of wild counterparts to cultivated plant species as well as useful tropical plants. Different warm and temperate zone species can also be found in gene pool centers.


Small Population Size

Smaller groups can act significantly than bigger groups. They are frequently the result of demographic shortages from larger populations, resulting in loss of heterozygosity and genetic diversity, as well as variant loss or fixation and changes in allele rates. A tiny population is more vulnerable to demographic and genetic chaotic events, which can have an effect on the population's long existence. As a result, small populations are frequently labeled endangered or extinct, raising conservation concerns.


The Founder Effect

The founder effect is the reduction of genetic differences that happens when a new species is founded by a limited number of people from a larger group, according to population genetics. Ernst Mayr was the first to thoroughly explain it in 1942, based on previous theoretical work by people like Sewall Wright. Since genetic variety has been lost, the resultant population may be genotypically and phenotypically diverse from the parent species from which it is produced. The founder effect is hypothesized to cause speciation and subsequent evolution of new species in severe circumstances.

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FAQs (Frequently Asked Questions)

1. What is the Gene Pool in Biology?

A gene pool is the total sum of the genetic diversity found in a population of a particular species. Thus, a large pool of genes will have extensive genetic diversity while a narrow gene pool will have low genetic diversity.

2. What is an Example of Gene Pool?

A gene pool is a collection of different genes, both expressed and not expressed, present in a population of a particular species. This can be any population in consideration for example frogs in a pond, trees in a forest, etc. The human population as a whole is also a gene pool and it is approximated that there is diversity in every allele of the approximately 20,000 genes found in the human genome. 

3. What is Genetic Drift?

The shift in the prevalence of a preexisting gene variant in a species owing to a random sampling of organisms is known as genetic drift.  The offspring's alleles or the existing genes are a sampling of the parents, and chance plays a part in deciding whether or not a specific individual lives and reproduces. The allele rate of a group is the proportion of copies of a gene that have the same form. Gene variations may vanish altogether due to genetic drift, reducing genetic variation. It can also lead previously uncommon alleles to become substantially more common, if not addressed.


When low copies of an allele are present, the influence of genetic drift is stronger, and when numerous copies occur, the impact is smaller. During the mid-twentieth century, there were heated disputes about the comparative impact of natural selection against neutral mechanisms such as genetic drift. Ronald Fisher, who used Mendelian genetics to explain natural selection, maintained the idea that genetic drift serves only a minor influence in creation, and this was the prevalent view for decades. Motoo Kimura, a population geneticist, reignited the discussion in 1968 with his unbiased theory of molecular evolution, which claims that genetic drift acting on neutral mutations is responsible for the majority of cases where a genetic change propagates along with a population, though it is not inevitably phenotypic changes.

4. What is Gene Flow?

Gene flow also known as gene migration or allele flow is the transmission of biological substances from one group to someone else in genetic studies. Two populations with similar allele rates can be regarded as a single functional population if the pace of gene flow is high enough. If the selection force is high enough, populations might diverge the process of selecting a subset even though they are swapping alleles. Gene flow is a crucial technique for spreading genetic variation from one population to another. By altering allele frequencies, migrants alter the distribution of genetic diversity across groups, the proportion of members carrying a particular variant of a gene. 


Gene transfer at high rates can minimize genetic diversity between the two groups, resulting in increased homogeneity.As a result, gene flow is assumed to limit diversification and restrict spreading by mixing the gene pools of the populations, reducing the formation of biological variations that would otherwise lead to divergence and adaptation. In exceptional circumstances, dispersal leading in gene flow can result in the introduction of novel genetic mutations into a species or population's gene pool.

5. What are the Genetic Effects of Small Population Size?

Conservationists frequently express concern about the destruction of genetic diversity in small populations. When working with small groups, there are two types of genetic change to consider: 

i) The percentage of an individual's loci that include homozygous instead of heterozygous alleles; the level of homozygosity within a community. Many damaging alleles are only dangerous when they are homozygous. 

ii) The degree of monomorphism or polymorphism inside a species; that is, how many distinct alleles of the same gene are found in a population's gene pool. Small populations are more affected by genetic drift and the chance of hybridization, which can result in diversification. 

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