Although it only occurs in very small populations, the consequences of its presence are severe. It happens as a result of a mistake in picking the alleles for the next generation from the gene pool of the present generation during the selection process. There is no evidence that it is caused by environmental factors. Due to the fact that the genes do not alter fitness and that there is no natural selection pressure against the alleles in large populations, allele frequency of the genes remains relatively steady in large populations.
Genetic Drift Bottleneck Effects Come in a Variety of Forms
The bottleneck effect occurs when the size of a population is drastically reduced as a result of competition, predators, or diseases.
Because the organisms that carry specific alleles are eliminated from a population, the frequency of certain alleles in that population changes. Because these are the only alleles left, the number of the others continues to grow.
This is found following natural disasters such as volcanic eruptions, earthquakes, and other similar events, which result in the death of the majority of the population.
This is referred to as the “Founder Effect.”
The founder effect occurs when a new population is established in a new site as a result of physical or geographical obstacles.
The newly generated population does not interact with or mate with the old population in any way.
Consequently, the allelic frequencies of the new population will be different from the allelic frequencies of the previous population.
There are numerous species that can only be found on a single island, and this is one of them. Because of the founder effect, for example, two birds of the same species may arrive at the same island. On that island, the alleles of those individuals will be accountable for the diversity.
These alleles will gain dominance, and mutations in the population will result in the emergence of new species as a result of selection. The new population will become so distinct from the old that they will no longer be able to interbreed.
Is There a Cause for Genetic Drift?
Generally speaking, genetic drift occurs in smaller populations than larger populations. A single allele can become extinct in a small population containing many different alleles. In a population with a large number of organisms, the likelihood of losing a whole allele is lower. This is due to the fact that the alleles are found in many creatures and that all of the alleles cannot be eliminated.
If an allele has an effect on the organism in such a way that it promotes more DNA replication, the frequency of the allele increases. If an allele causes harm to the organism, the frequency of that allele declines. Genetic drift is defined as the increase or decrease in the frequency of an allele as a result of the presence of that allele in a random organism that has survived.
Let us consider a population of rabbits that has both brown and white fur, with white fur being the dominant allele in the brown fur population. Due to genetic drift, it is possible that only the brown population may survive, with all of the white individuals being exterminated.
Brown and blue eyes are shared by a spouse who has children with either brown or blue eyes. Because brown eyes are the dominant allele, even if there is a 50% possibility of having blue eyes, it is possible that all of the children will have brown eyes in future generations as a result of chance.
A bird has two different-sized beaks because of an allele that it possesses. Genetic drift may result in the extinction of one of the beak sizes from the population, hence diminishing the genetic diversity of the bird population’s gene pool.
Consider the possibility of a plant that produces blue or yellow blossoms. Suppose a fire destroys the yellow flowers on a plant and the blue gene becomes dominant; the plant will then produce exclusively blue blooms.
Genetic Drift as opposed to Gene Flow
It is the transfer of genes between populations, species, or creatures that is known as gene flow. Bacteria, for example, have the ability to transfer genes between distinct cells. Genetic drift, on the other hand, is the term used to describe the random selection of genes in a population.
It is known as gene flow when individuals from one population migrate to another and reproduce in that new location (or populations).
Conclusion
The term “genetic drift” refers to the process of genes being passed down from one generation to the next. The following are some examples of how genetic drift might be observed: The American Bison was once so heavily hunted that it was on the verge of extinction. The genetic diversity of the population that has survived to this day is extremely limited.