What is genetic drift

A subdivided population adaptation is a process consisting of two phases, the first phase is genetic drifting where the loss or fixation of some alleles randomly occurs by chance which in turn helps the population to explore new genes, the second phase is characterized by natural selection of the most beneficial genes that were introduced in phase one, these genes are exported to other populations by migration.

The genetic drift theory has a significant role in the evolutionary process of individuals where the balance between mutations and gene drifting creates a state in genetic variation. Since mutations introduce new alleles while gene drifting may eliminate or fix the new alleles. According to Charles Darwin's theory of natural selection, preferable genes are favored by nature in the gene pool, and over time, these preferable characteristics become more exclusive in the gene pool.

This tutorial rounds up all the factors that can alter the makeup of a gene pool Read More. This lesson looks at population attributes, regulation, and growth. It also covers population genetics, particularly genetic variations, natural selection, genetic drift, genetic migration, and speciation Skip to content Main Navigation Search. Dictionary Articles Tutorials Biology Forum. Table of Contents. Biology definition: Genetic drift is the drifting of the frequency of an allele relative to that of the other alleles in a population over time as a result of a chance or random event.

An example where the effect of genetic drift is magnified is the so-called bottleneck effect. Synonyms: allelic drift; Sewall Wright effect. Quiz Choose the best answer. The process of change in the frequency of an allele gene variant in a population over time. Genetic frequency. Genetic mutation.

Figure 5. The probability that an allele will drift away in any single generation in a two-allele model with different initial frequencies and different effective population sizes.

The consequences of genetic drift are numerous. It leads to random changes in allele frequencies. Drift causes fixation of alleles through the loss of alleles or genotypes. Drift can lead to the fixation or loss of entire genotypes in clonal asexual organisms.

Drift leads to an increase in homozygosity for diploid organisms and causes an increase in the inbreeding coefficient. Drift increases the amount of genetic differentiation among populations if no gene flow occurs among them. Genetic drift also has two significant longer-term evolutionary consequences. Genetic drift can facilitate speciation creation of a new species by allowing the accumulation of non-adaptive mutations that can facilitate population subdivision.

Drift also facilitates the movement of a population from a lower fitness plateau to a higher fitness plateau according to the shifting balance theory of Sewall Wright. The amount of population subdivision is expected to increase because of the random losses of alleles that occur in different populations. In addition, random changes in allele frequencies are expected to occur in different populations, and these random changes tend to make populations become differentiated.

Finally, small effective population sizes increase the likelihood that mating events will occur between close relatives, leading to an increase in inbreeding and subsequent loss of heterozygosity.

In agroecosystems, pathogen populations usually become very large as a result of the genetic uniformity of the host plant, so genetic drift may not play a large role in the evolutionary process within a farmer's field in the real world. Few experiments have been conducted to test this hypothesis. But there is lots of evidence for founder effects in agroecosystems, especially in Australia, because it was the continent most recently colonized by Europeans who introduced first their crops and then their crop diseases.

In natural ecosystems, genetic drift may play a more prominent role in the evolution of pathogens because host populations are genetically diverse and have a patchy distribution, so pathogen population sizes are not so large, and bottlenecks probably occur frequently in these natural populations. We will return to this theme after introducing the concept of metapopulations. Mycosphaerella graminicola causes Septoria tritici leaf blotch on wheat. In each generation, some individuals may, just by chance, leave behind a few more descendants and genes, of course!

That, in a nutshell, is genetic drift. Earlier we used this hypothetical cartoon. This article has been posted to your Facebook page via Scitable LearnCast.

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