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Genetic Drift mainly deals with the significance of the great change marked by an error in selecting the allele from the gene pool. Its effects are really strong though it occurs in a small number of populations. Environmental influences do not impact this. In this article, we will explore types of genetic drifts, their examples, characteristics, and their causes.
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Keyterms: Allele, Environmental influences, Gene, Dominant allele, Population, Natural selection, Food cycle, Environment, Genetic drift, Evolution
Read More: Mechanism of Evolution
What is Genetic Drift?
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Scientists have conducted multiple kinds of research and studies in biology in order to define the concept of Genetic drift. The process of an evolutionary change in the allelic frequencies of a group of populations is termed genetic drift.
- It has been claimed that such changes in the allelic frequencies of a group of population generally occur by chance rather than any specific detrimental causes.
- The use of the words ‘group of population’ simply symbolizes the range of population on which the effect of genetic drift is usually witnessed.
- For instance, it occurs only to a very small proportion of the entire population, although, the effects of the genetic drift are stronger and remain intact for a longer period of time.
- However, the genes do not affect fitness as a whole and it does not have a natural selection pressure against the alleles. And therefore, the allele frequency of the genes in the larger populations remains quite stable.
Genetic Drift Examples
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For a better understanding of the genetic drift, some of the instances of the genetic drift are mentioned below.
- Any parent with blue and brown eyes might have children with brown or blue eyes. But if the dominant allele will be the brown color of the eyes, then, there might be chances that the children will also have only brown eyes in the future and the same color of the eyes will be continued for generations, thus, making the genes of the blue eyes as recessive.
- Let us now take the example of the rabbits. Assuming the population of rabbits with brown fur and white fur and considering the white fur being the dominant allele. But the genetic drift will impact the dominant allele and only the brown population might remain, leading to the elimination of the rabbits with white fur.
- Another example is the American Bison. Their population was once hunted to such an extent that it became endangered. And as per the researchers, the population which has recovered now does not have enough genetic variations.
- A bird with an allele of the two different sizes of beaks. Thereby, genetic drift might impact the sizes of the beaks of the bird in a way by eliminating one of the beak sizes from nature, thus, reducing the genetic variations of the birds.
- The same instance of genetic drift could also be seen in the case of the plants. Considering a plant that blossoms the flowers are either of blue color or of yellow color. Thereby, genetic drift might eliminate one color and make the other the dominant one.
There can be multiple instances of genetic drift around us and it can be observed in all the forms of life facilitating the reproduction process.
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Types of Genetic Drift
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The process of genetic drift can be categorized into two main types:
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Bottleneck Effect
- This type of genetic drift is characterized by the natural phenomenon of population elimination of the weaker allele.
- In such cases, the population size severely decreases due to the factors of competition, predators, or diseases, indicating the concept of ‘survival of the fittest’.
- Therefore, this elimination results in a change in the frequency of the allele.
-
Founder Effect
- Under this effect, a new population emerges at some new location due to the specific habitat or the physical or geographical barriers.
- Since this new population is not a part of the food cycle or the food web of that area, the allelic frequencies of the new population will be different from the original population.
- This might further lead to the process of interbreeding and it shall contribute to enriching the diversity of any area or habitat. Although, there might be a situation when the new population will diverge to an extent that they might prevent from indulging in the process of interbreeding.
Causes of Genetic Drift
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Genetic drift usually occurs as a result of the natural phenomenon mentioned above. Sometimes, it also occurs due to some erroneous act in the selection of the alleles for the next generation from the given gene pool of the current generation.
The dominance of any particular type of DNA in the genes of the population might also contribute to genetic drift. Although, scientists have made it clear that environmental circumstances do not contribute to genetic drift.
Read More: Evidence For Evolution
Genetic Drift vs Gene Flow
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There are some differences between gene flow and genetic drift. Such as,
- When we talk about Gene flow, it is always considered as the flow or the movement of genes and this movement ultimately takes place between the different populations, species, or maybe different organisms. Usually, when the migration occurs between the individuals from one population and breed, gene flow takes place. For instance, there can be a transfer of genes between the different cells of bacteria themselves.
- While the genetic drift could be a more random change in the gene of a specific group of population. The importance of the evaluation of the allele frequency is a significant part of it.
Things to Remember
- Genetic drift is usually considered as a random change in the gene of a group population which has intense effects on the larger population in the future.
- Genetic drift, if occurred, is capable of impacting the population very intensely. The effects of genetic drift are visible in the upcoming generations.
- It only impacts a smaller proportion of the entire population and can affect plants, humans, and animals.
- Usually, the error in the DNA or the allele selection from the gene pool works as the main cause of genetic drift.
- The environment does not contribute to the occurrence of genetic drift but the environmental factors definitely do the same by giving birth to a new type of dominant species in a habitat that might function as an invasive – alien species.
- Genetic drift and the invasive-alien species have the capability of hampering the entire ecosystem and habitat intensely.
- The bottleneck effect is characterized by the natural phenomenon of population elimination of the weaker allele.
- In the foundation effect, a new population emerges at some new location due to the specific habitat or the physical or geographical barriers.
Read More: Heredity and Evolution
Previous Year Questions
- Which among the following was the biggest land dinosaur?...[KCET 2020]
- A good example for recapitulation theory is/are
- Which one of the following organs are homologous?
- An experiment to prove that organic compounds were the basis of life was performed by:
- Example of analogous organs is:
- Which one is not a vestigial organ in man?
- Age of fishes is also known as...[JKCET 2011]
- Mammal like reptiles evolved during….[AMUEEE 2012]
- Evolution of different species in a given area starting from a point and spreading to other geographical areas is called...[JKCET 2015]
- Vestigial organs present in an adult individual are example of basis of evidence of evolution...[JKCET 2007]
- The theory of random genetic drift was proposed by...[JKCET 2007]
- Biogenetic law as given by Haeckel states that….[AMUEEE 2012]
- This kind of change in the gene pool is called a...[JKCET 2012]
- Transformation of the early reducing atmosphere of the earth into an oxidizing atmosphere was mainly due to the activities of...[KCET 2008]
- The brain capacity of Homo habilis...[KCET 2019]
- According to Darwin, evolution is_______...[KCET 2010]
- By the statement "Survival of the Fittest" Darwin meant that...............[KCET 2011]
- The idea of Natural Selection as the fundamental process of evolutionary changes was reached….[KCET 2007]
- Coarcervates were experimentally produced by,…..[KCET 2004]
- Find the mis-match from the following pairs :….[KCET 2016]
Sample Questions
Ques. Define genetic drift with examples. (3 marks)
Ans. The process of an evolutionary change in the allelic frequencies of a group of populations is termed genetic drift. It has been claimed that such changes in the allelic frequencies of a group of the population generally occur by chance. For example. consider a bird with an allele of the two different sizes of beaks. Thereby, genetic drift might impact the sizes of the beaks of the bird in a way by eliminating one of the beak sizes from nature, thus, reducing the genetic variations of the birds.
Ques. Explain the role of the environment in the procedure of genetic drift? (3 marks)
Ans. The environment alone does not contribute to the occurrence of genetic drift but the environmental factors definitely do the same by giving birth to a new type of dominant species in a habitat known as an invasive – alien species. In the presence of such species, the population size severely decreases due to the factors of competition, predators, or diseases, indicating the concept of ‘survival of the fittest.’ Therefore, this elimination results in a change in the frequency of the allele.
Ques. Illustrate the causes of genetic drift. (2 marks)
Ans. Genetic drift usually occurs as a result of the natural phenomenon. Sometimes, it also occurs due to some erroneous act in the selection of the alleles for the next generation from the given gene pool of the current generation. The dominance of any particular type of DNA in the genes of the population might also contribute to genetic drift.
Ques. Explain the bottleneck effect? (2 marks)
Ans. The Bottleneck Effect is one type of genetic drift which is characterized by the natural phenomenon of population elimination of the weaker allele. In such cases, the population size severely decreases due to the factors of competition, predators, or diseases, indicating the concept of ‘survival of the fittest.’ Therefore, this elimination results in a change in the frequency of the allele.
Ques. What are the two types of genetic drift? Explain. (4 marks)
Ans. The process of genetic drift can be categorized into two main types:
- The Bottleneck Effect is characterized by the natural phenomenon of population elimination of the weaker allele. In such cases, the population size severely decreases due to the factors of competition, predators, or diseases, and such eliminations result in the change in the frequency of the allele.
- Another type of genetic drift is Founder Effect. In this, a new population emerges at some new location due to the specific habitat or the physical or geographical barriers. This new population is not a part of the food cycle or the food web of that area and therefore, the allelic frequencies of the new population will be different from the original one. Thus, leading to the process of interbreeding. Although, there might be a situation when the new population will diverge to an extent that they might prevent from indulging in the process of interbreeding.
Ques. What is gene flow? Explain how is it different from Genetic drift? (3 marks)
Ans. Gene flow is considered as the flow or the movement of genes and this movement ultimately takes place between the different populations, species, or maybe different organisms. Usually, when the migration occurs between the individuals from one population and breed there, gene flow takes place.
For instance, there can be a transfer of genes between the different cells of bacteria themselves. While the genetic drift could be a more random change in the gene of a specific group of population. The importance of the evaluation of the allele frequency is a significant part of it.
Ques. Explain Founder Effect in the context of genetic drift. (3 marks)
Ans. Under the founder effect, a new population emerges at some new location due to the specific habitat or the physical or geographical barriers. Since this new population is not a part of the food cycle or the food web of that area, the allelic frequencies of the new population will be different from the original population. This might further lead to the process of interbreeding and it shall contribute to enriching the diversity of any area or habitat. Although, there might be a situation when the new population will diverge to an extent that they might prevent from indulging in the process of interbreeding.
Ques. Mention two examples of genetic drift with an explanation. (3 marks)
Ans. One example of genetic drift in the context of human beings while the other for animals is as:
- If any parent with blue and brown eyes might have their children with brown or blue eyes. But if the dominant allele will be the brown color of the eyes, then, there might be chances that the children will also have only brown eyes in the future and the same color of the eyes will be continued for generations, thus, making the genes of the blue eyes as recessive.
- Taking another example of the rabbits. Assuming the population of rabbits with brown fur and white fur and considering the white fur being the dominant allele. But the genetic drift will impact the dominant allele and only the brown population might remain, leading to the elimination of the rabbits with white fur.
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