Genetic Drift

Introduction

Gene flow refers to the transfer of individual genetic material from one person to another. There are many types of events involved in this process, such as people moving to a new area or pollen being driven to a new location. It can lead to significant genetic variation if the versions of gene flow are passed to a population that does not have the gene versions.

Migration between two popular places can also cause a change of allele frequencies. This refers to a percentage of people who have a particular variant or gene. The addition of genetic variants can also occur in this immigration.

Factors Affecting Gene Flow

Many factors influence gene flow between different populations. Mobility is one of these important factors. The potential to migrate is determined by how mobile an individual is. Although animals are more mobile than plant, seeds and pollen can still be transported longer distances by animals and wind.

A combination of two gene pools can result in constant gene flow between populations, which reduces genetic differentiation between different groups. Gene flow works against speciation by combining two populations’ gene pools and resolving genetic variations that could lead to full speciation or the development of new species.

The pollen of grass species that grow along either side of a highway is likely to migrate from one side to the other. If the pollen can fertilise the plant at its termination and form viable offspring, the pollen’s alleles have the ability to shift from one population to the other.

Genetic Drift

What is Genetic Drift?

Genetic drift refers to an evolutionary change in the allelic frequencies of a group as a matter of chance. Although it is rare, its effects can be severe in small populations. It is caused by an error in choosing the appropriate alleles from the current generation. It is not caused by environmental factors.

Large populations tend to have stable allele frequencies because genes do not affect fitness or face natural selection.

Different Types of Genetic Drift

Bottleneck Effect

The bottleneck effect is a drastic decrease in population size due to competition, predators or diseases.

Certain alleles are more common in certain populations because they are no longer carried by organisms. They are the only remaining alleles, so they increase in number.

This can be observed in natural disasters such as earthquakes and volcanic eruptions. This can lead to the death of most of the population.

The Founder Effect

The founder effect is when a new population is established in a new area due to geographical or physical barriers.

The new population shows an increase in inbreeding.

The allelic frequencies of this new population will therefore be different to the original.

Many species are only found on one island. This is because of the founder effect. Two birds from the same species can reach an island. The island will have diversity because of their alleles.

These alleles will prevail and mutations in the populations will result in new species. They will not interbreed anymore as the new population will be so diverse.

What causes genetic drift?

In smaller populations, genetic drift is more common. Any of the alleles could become extinct in a small population that has many alleles. There is less chance that an allele will be lost in a large population. Because many organisms have the alleles, it is impossible to wipe them all.

The allele frequency will increase if the allele causes more DNA replication. The allele frequency will decrease if the allele causes harm to the organism. Genetic drift is when the allele frequency changes or decreases due to its presence in an organism that has survived.

Example of Genetic Drift

These examples show genetic drift:

• American Bison was once the most hunted, making it an endangered species. Today, there are very few genetic variations in the population that have recovered
• Imagine a population with white fur and brown fur. White fur is the dominant allele. Genetic drift can lead to the elimination of all white rabbits, leaving only the brown ones
• If a couple has blue and brown eyes, they have children with blue or brown eyes. Even though there’s a 50% chance that the child will have blue eyes, the dominant allele is brown. This means that all children could inherit brown eyes from their parents
• An allele can be assigned to a bird for one or both sizes of beaks. One of the beak sizes might be eliminated by genetic drift, which could reduce the genetic variation of the bird’s gene pool
• Hypothesize a plant that produces yellow or blue flowers. If the yellow flowers are burned in a fire, and the dominant blue allele is present, the plant will only produce blue flowers

Genetic drift vs. Gene flow

Gene flow refers to the movement of genes among populations, species, and organisms. E.g., bacteria can transfer genes between different cells. Genetic drift, on the other hand, refers to a random selection of genes within a population.

Gene flow is when individuals from one population move to another population and breed there.

Gene flow, unlike genetic drift, does not assess allele frequencies.