Genetic Drift: Definition, Types, Examples and Process

Genetic drift is the random change in allele frequencies within a population from generation to generation, often due to chance events. Genetic drift favours features that may improve survival or reproduction and at the same time, genetic drift does not depend on an allele's advantage and occurs more strongly in smaller populations. This process can cause some alleles to become fixed, while others are lost, reducing genetic variation. This is one of the important topics of Genetics in Biology.

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This Story also Contains

1. Definition of Genetic Drift
2. Basics of Genetic Drift
3. Types of Genetic Drift
4. Genetic Divergence Between Populations
5. Genetic Drift Vs Gene Flow

Definition of Genetic Drift

Genetic drift is a process that causes changes in allele frequencies within a population. Its major sources are generally identified as chance events, especially in small populations. Unlike natural selection, which depends on differential survival and reproduction, genetic drift is a random operator, which might sometimes result in the loss or fixation of alleles over time.

Definitions of genetic drift also says about its ability to change genetic patterns, hence affecting the evolutionary outcome of species or species with lower population sizes and isolated ones. For example, in a small population, a rare allele may become extinct due to random events. The element of randomness gives one much insight into how populations change through the evolution processes.

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Basics of Genetic Drift

Genetic drift is an evolutionary process that is based on randomness. It causes the shifting of allele frequencies in a population because the survival and reproduction of individuals depend on chance events, hence producing fluctuations in allele frequencies among generations.

Genetic Drift Vs. Natural Selection

While both genetic drift and natural selection affect the evolution of a population, they work in different ways. For the process, survival and reproduction are contingent upon an allele's efficiency in enhancing these functions. Genetic drift, on the other hand, is a strictly random process, unrelated to allele efficiency. Both processes play crucial roles in the process of evolution, though they work in different ways.

Types of Genetic Drift

Bottleneck Effect

The bottleneck effect involves the situation where an event such as a natural disaster or disease causes a massive reduction in population size. This drastic reduction in population limits the gene pool and thus lowers genetic variation levels substantially. As an example, northern elephant seals have relatively low genetic variation levels today due to their population size dropping to less than 100 in the 19th century, while their current numbers are in the tens of thousands.

Founder Effect

The founder effect takes place when a small group of individuals breaks away from a larger population to form a new population. The small population, therefore, possesses only a fraction of the genetic diversity of the original population. For example, isolated populations such as the Amish contain less genetic variation and are therefore more prone to genetic disorders.

Genetic Divergence Between Populations

Genetic drift also causes genetic divergence between populations, usually when they are isolated or separated geographically and are unable to interbreed. As time progresses, the actual random changes in allele frequencies create genetic differences, and this may eventually lead to speciation, depending on the degree of differentiation.

Genetic Drift Vs Gene Flow

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