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Gene flow is the movement or transfer of genes from one population to another. Genes are one of the most crucial components of the human body. They carry the genetic information in the organisms and pass it on from one generation to the next one.
- Gene Flow is also called Gene Migration.
- In humans, genetic information is carried in the form of chromosomes.
- If the gene flow is high then the frequency of population also increases.
- Population tends to diverge when they are exchanging alleles.
- Thus, gene flow affects the genetic diversity within a population.
- Gene regulation is one of the processes involved in gene replication and expression.
- Gene regulation refers to switching the genes on and then off.
Read More: Binary Fission
Key Terms: Gene flow, Gene Migration, Gene, Chromosomes, Gene replication, Pollination, Plant, Genetic variation, Reproductive Organs
What is Gene Flow?
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Gene flow is a popular and individual generic material that transfers from one population to another. The process involves different events like pollen transferred from one place to another.
- Gene Flow changes the composition of the gene pool of the population.
- The process increases variability within the population.
- Gene flow changes the local allele frequency in the human population.
- It can take place between similar species by vertical gene transfer process.
- The flow can take place between dissimilar species by the horizontal gene transfer process.
- If the version of gene flow is carried in a population where the version of the gene doesn't exist.
- In that case, it can form a source of genetic variation.
- Gene flow can be seen in plants, which is also called pollination.
Gene Flow
Read More: Chromosomal Theory of Inheritance
Factors influencing Gene Flow
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The factors that are inflencing the gene flow are as follows:
Mobility of Gene Flow
Gene flow is expected to be a lower species that has low dispersal or mobility. The process occurs in fragmented habitats, where there is a long distance between populations and when there are small population sizes.
- Constant gene flow between two populations can lead to a combination of two gene pools.
- This, in turn, minimizes the genetic differentiation between two groups.
- Mobility plays an important role in the dispersal rate.
- Highly mobile individuals tend to have greater movement prospects.
- Animals are thought to be more mobile than plants.
- Pollen and seeds can be carried out to great distances by animals, water, or wind freely.
- When the flow is impeded, there can be an increase in inbreeding, measured by the inbreeding coefficient (F) within a population.
Read More: Genetic Drift
Environmental Factors of Gene Flow
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In some cases, environmental factors may also lead to gene variations in a population. Let's take a situation if an island has very little vegetation, the birds who live there for a long period. They were habituated to consume food grains, but now, they will have to be habituated to eat insects. Therefore, with the period and their physical appearances, the genetic makeup between the two groups of birds will become different.
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Factors that Prevent Gene Flow
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Some restrictions that prevent Gene Flow in population are as follows:
Geographical Barriers
Sometimes, geographic barriers such as continental drift, deserts, vast oceans, and high mountains prevent migration in and out of the population. If the population is isolated for a long time, then its genes may diverge significantly from other related groups.
- In a situation when the members of the isolated group are not able to reproduce with any other community.
- In that case, they will be considered as an altogether separate species.
- Other human activities, such as cutting down forests and building dams, also lead to a large number of geographical isolations between species.
Geographical Barrier
Reproductive Barriers
Another factor that prevents gene flow is the reproductive Barrier. Other than external restrictions, there are also internal barriers in the form of reproductive organs that prevent the gene flow between species.
- Several species have evolved to form different reproductive organs, which prevent mating with each other.
- In addition, various species have different mating seasons and mating rituals or calls, which has resulted in reproductive isolation.
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Gene Flow Between Species
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There are two types of gene flows that take place among the species which are as follows:
Horizontal Gene Transfer
Horizontal Gene Transfer refers to the transfer of genes between organisms in a manner other than traditional reproduction method. It can be done either through transformation, conjugation, transduction, or GTA-mediated transduction.
- Viruses can transfer genes between species.
- Bacteria can incorporate genes from dead bacteria.
- It can exchange genes with living bacteria and can exchange plasmids across species boundaries.
Hybridization
It is the process of inbreeding individuals from a genetically different population so that they can produce a hybrid. This exchange is always clear cut, for sometimes the hybrid might look identical to the original species phenotypically, but upon testing the DNA, it is apparent that hybridization has occurred.
Read More: Allele
Examples of Gene Flow
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Some examples of gene flow are as follows:
Fragmented Population
Fragmented landscapes such as the Galapagos Islands are an ideal place for adaptive radiation to occur as a result of differing geography. Darwin's finches likely experienced that allopatric speciation in some part due to differing geography. But it doesn't explain why we see so much different kinds of finches on the same island. Gene flow moves in the direction of where the recourses are abundant.
Island Population
Due to geographic isolation, gene flow between the two species was limiting and differing environments caused the marine iguana to evolve to adapt to the island environment. For instance, they are the only iguana that has evolved the ability to swim.
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Things to Remember
- Gene flow effects in reducing genetic differences between populations.
- Allele frequencies can change when individuals leave or join the population as a result of gene flow.
- Gene Flow takes place through the movement of population from one place to another through a process of migration.
- Two main barriers prevent Gene Flow: Geographical Barriers and Reproductive Barriers.
- Gene flow and natural selection are the two evolutionary forces which act as a stuff of evolution.
Sample Questions
Ques: Give a basic definition of gene flow? (2 marks)
Ans: The movement of genes from one population to another population is known as Gene Flow. This process involves various events in its such as pollen transferred from one place to another place and many more. It is also involved in gene replication and gene expression.
Ques: Give an example of gene flow? (2 marks)
Ans: One example of gene flow can be seen in plants which is the process called pollination in plants. Other examples of gene flow includes fragmented population, island population and many more. Due to geographic difference, gene flow between various species get limited.
Ques: What is Horizontal Gene Transfer? (2 marks)
Ans: It is a type of gene flow that takes place between species or organisms which is different from traditional reproduction. It would be said as transformation, conjugation, transduction, or GTA-mediated transduction. It is also known as laterla gene transfer.
Ques: How does gene flow affect a population? (2 marks)
Ans: The effect of gene flow is to reduce genetic differences between populations, thereby delaying or preventing evolution of the population in different geographical areas into separate species of the pathogen. In such cases, genes may diverge significantly from other related groups. As a result new species is formed whichwill be considered as an altogether separate species.
Ques: What do you mean by genetic drift? (2 marks)
Ans: Genetic drift is a process in which some individuals have more offspring than other individual, and it would change allele frequencies which are random in direction. It can change as a result of gene flow. It causes genes to disappear completely thus reducing genetc variation. It first effect the species of allele. In case few copies of allele exist then drift is more visible among organisms.
Ques. What is the difference between vertical gene transfer and horizontal gene transfer? (3 marks)
Ans. The difference between vertical gene transfer and horizontal gene transfer are as follows:
| Vertical Gene Transfer | Horizontal Gene Transfer |
|---|---|
| Vertical gene transfer take place between population of same species. | Horizontal Gene Transfer take place between population of different species. |
| In this whole genome is transferred. | In this ony few genes are transferred. |
| The process take place through asexual or sexual production. | The process take place through transduction, or GTA-mediated transduction. |
Ques. Explain: (A) Allele
(B) Genotype
(C) Heterozygous dominant (3 marks)
Ans. (A) Allele: An allele is one or two variation of same DNA sequence found at the locus. Locus is defined as the location of any gene or genetic material on a chrosomes.
(B) Genotype: Genotype is defined as the type of variant found at a particular location in a genome. It consists of complete set of genetic material.
(C) Heterozygous dominant: Genotype conisting of different type of alleles and shows the characteristic of the dominant gene is called Heterozygous dominant.
Ques. How mobility factor affect gene flow? (3 marks)
Ans. In case the value of mobility within gene is low in that case the gene flow is lower in species.The process is carried out in fragmented habitats, where there is a long distance between populations and when there are small population sizes. It also affects the dispersal rate. Low mobility minimizes the genetic differentiation between two groups. Individuals tend to have greater movement prospects if their mobility is higher.
Ques. What is the difference between monohybrid and dihybrid? (3 marks)
Ans. The difference between monohybrid and dihybrid are as follows:
| Monohybrid | Dihybrid |
|---|---|
| Monohybrid is study about single species. | Dihybrid is study about two or more species. |
| It is used to study about inheritance process in single pair of allele. | It is used to study about inheritance process in two or more pair of allele. |
| It determines the dominance of genes. | It determines the assortment of offspring. |
Ques. What is law of dominance? (2 marks)
Ans. Law of Dominance states that if two parents are involved in mating and differ in only one genetic characteristic then all offspring in the first generation are equivalent to examined characteristic in the genotype. According to the law, the dominant allele will cause the recessive allele to be masked. The law was proposed in heterozygote state by Mendel.
Ques. What is the difference between Homozygous and Heterozygous? (3 marks)
Ans. The difference between Homozygous and Heterozygous are as follows:
| Homozygous | Heterozygous |
|---|---|
| Homozygous involves two similar types of allele in a particular trait. | Heterozygous involves two disimilar types of allele in a particular trait. |
| In this process only one gamete is produced. | In this process two or more gamete is produced. |
| In this process genotype is either dominant or recessive. | In this process genotype is both dominant or recessive. |
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