GENETIC DRIFT (Syllabus: GS Paper 3– Sci and Tech)
Context: Genetic drift, not natural selection, was recently identified as the main factor driving speciation in endangered pupfish species.
Genetic Drift
- Definition: It is an evolutionary change in allelic frequencies of a population as a matter of chance.
oGenetic drift describes random fluctuations in the numbers of gene variants in a population.
oIt takes place when the occurrence of variant forms of a gene, called alleles, increases and decreases by chance over time.
oThese variations in the presence of alleles are measured as changes in allele frequencies.
- Population Size: It occurs in very small populations, but its effects are strong.
- Cause: Occurs due to an error in selecting the alleles for the next generation from the gene pool of the current generation.
- Environmental Independence: It does not occur due to any environmental influences.
- Stability in Large Populations: In large populations, the allele frequency of the genes remains relatively stable because the genes are not affecting fitness and do not have a natural selection pressure against the alleles.
- Types of Genetic Drift
oBottleneck Effect: Population size severely decreases due to competition, predators, or diseases.
oFounder Effect: A new population is founded in a new location due to physical or geographical barriers. The new population formed does not interact and mate with the original population.
Gene Flow
- About: Gene flow entails the transfer of genes among populations, species, or organisms, exemplified by bacterial gene transfer. Conversely, genetic drift involves the random selection of genes within a population.
- Migration: Gene flow arises when individuals migrate from one population to another and interbreed.
