Genetic Drift: Definition, Types, Examples and Process

What Is Genetic Drift?

Genetic drift is the process that shows changes in the allele frequency in a population in a particular generation usually depending on chance factors, especially in a small population size. Thus, while natural selection is based on factors of differential survival and reproduction, genetic drift works through random, chance fluctuations leading to the loss in time of alleles or their fixation.

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In genetics, genetic drift is important because it is the mechanism whereby the process may alter the genetic patterns and apprehend the pathogen's model of the evolution of species, notably those which are limited or reclusive. This article presents genetic drift as a culmination of various factors and studies its impact on populations and evolution outcomes to show that, in evolution, randomness plays a crucial role.

Basics Of Genetic Drift

• That means genetic drift is a random process of evolution which causes the shift of allele frequencies in a population.

• It happens because random events affect the survival and reproduction of people, thus, changing the frequency of alleles in successive generations.

Key Features Of Genetic Drift

Random Changes in Allele Frequencies: In this change of allele frequencies across generations, genetic drift outcomes are unpredictable. This randomness results in fixation or loss of alleles, and this implies that some alleles will not exist in the population while others will be overrepresented in the population.

Impact on Small Populations: The ability of the relative chance fluctuations within the field of allele frequency is particularly felt in rather small populations. Hence genetic drift may result in large changes in genotypes and reduced genetic variation in small populations more so than within large ones.

Genetic Drift Vs. Natural Selection

• Like natural selection, genetic drift affects the architecture of populations, however, this process is not dependent on an allele's ability to increase survival and reproduction.

• Thus, natural selection promotes adaptations and increases the probability of the advantageous allele, while genetic drift derives the analysed changes to the chance factors unrelated to the efficiency of alleles.

• It is similar to the previous pair since both determine evolutionary outcomes, just in rather different manners.

Types Of Genetic Drift

Genetic drift is categorised as:

Bottleneck Effect

The bottleneck effect is defined as the situation where a certain population is faced with a severe decrease in numbers as a result of a disaster (for instance, natural calamities or diseases). This drastic reduction hinders the pool of genes and dents the genetic variation it in a very big way. For instance, while the current population number of a northern elephant seal can be in the tens of thousands, the early 19th-century population was of fewer than one hundred such seals as a consequence of which the latter had a low genetic variation in comparison to the former.

Impact on Genetic Diversity

The bottleneck effect lowers the population’s hereditarian variation because the species convey a limited number of the preceding group’s variation. The effect of these splits is the reduction of gene pool strength which can allow inbreeding and raise the possibility of genetic disorders.

Founder Effect

The founder effect involves a particular population that is initiated starting with a small group of people from a larger population. This small group contains only a part of the genetic variation that existed in the large population of the organism. For instance, a study of the isolated populations, especially the Amish people, come from a small population with little genetic variation; therefore, genetic disorders are quite rampant in such populations.

Impact on Genetic Variation

Hence, genetic variation is necessarily lower in the new population because certain traits vested in the founders become more prevalent, while other traits may disappear altogether. This may lead to a different gene pool from that found in the source population and the conditions for making the squid into a different species are without doubt met.

Mechanisms Of Genetic Drift

The mechanism of genetic drift includes:

Random Sampling Of Alleles

Genetic drift works through chance events of alleles being passed from parents to offspring; this results in the change of allele frequency in the population. Hence, when people reproduce, they produce descendants based on their alleles randomly, regardless of their nutritional value or population selection. This can result in random changes in allele frequencies within respective populations and hence alter the genetics string of the society over the period.

Role Of Population Size

There are several factors which influence the effect of genetic drift of which population size is notable. Small population sizes are more greatly influenced by random sampling effects hence larger shifts in allele frequencies within such a small population size will be greatly affected. However, in large populations, genetic drift is not very prominent since a large number of individuals makes it difficult for the population's allele frequency to be greatly affected by random events.

Effects Over Generations

Hence, over multiple generations, an extraordinary differentiation of the frequency of alleles can be observed in a population. In small populations, this leads to a reduction of genetic variation and fixation of certain alleles with no variation. This eventually cumulates to reduced genetic variation within the population and also increased rates of genetic disorders within the subpopulation as well as divergence of the populations.

Consequences Of Genetic Drift

Genetic drift can cause:

Loss Of Genetic Variation

Genetic drift always tends to fix the genotype by reducing genetic variation within the population. Random changes in allele frequency may well mean that some alleles will become rare and/or even vanish altogether which will be detrimental to the genetic variety. This loss may expose populations to environmental shifts and diseases hence reducing population fitness.

Fixation Of Alleles

Eventually, genetic drift may lead to alleles becoming fixed, which is a condition whereby a given allele becomes the only one in a population. At this point all the people in the population will have this allele hence the frequency is at 1. The results of this process may lead to a decrease in genetic variability and the ability to control the population’s evolution.

Genetic Divergence Between Populations

Genetic drift results in change and variation in genetic differences between populations especially when they are isolated geographically or in their ability to breed. Through time, fluctuations in allele frequencies by mere chance make populations inherited differently and, therefore, pose a potential for speciation depending on the degree of differentiation.

Table: Comparison Of Genetic Drift Effects In Small Vs. Large Populations

Examples Of Genetic Drift in Natural Populations

Northern Elephant Seals

The population of the northern elephant seal at that time had a low number: less than 100 during the 19th century they eliminated them through hunting. This extreme reduction affected the genetic variation and made the present population demonstrate less genetic variation as compared to the pre-bottleneck population. The seals’ gene pool confirms this past effect by bottlenecking; the majority of its alleles have been lost or fixed due to drift.

Amish Population (Ellis-van Creveld Syndrome)

For instance, the S mourning Amish community in Pennsylvania is generated from a small population; therefore, it exemplifies the founder effect, a form of genetic drift. Because the Amish individuals are rather reclusive and have a small gene pool, some congenital diseases, such as Ellis-van Creveld syndrome are more common among them. This particular syndrome: affecting bone growth and heart development is right on the heels of the reduced genetic variation in the population

Genetic Drift Vs Gene Flow

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