Gendrift is a change in allele frequency within a gene pool of a population. In this context, gene drift is usually triggered by a random event, such as a natural disaster, the shifting of continental plates, or the eruption of volcanoes. Thus, gene drift represents an evolutionary factor.
What is gendrift?
Gendrift represents an important factor in the formation and transmission of new genetic adaptations to the environment. In a way, gene drift represents the opposite of natural selection. This is because natural selection does not occur randomly. Instead, changes in the genes of a population are dependent on the reproductive and survival success of individual members of the population. They express their adaptability to the environment. On the other hand, gene drift has no such reasons, but occurs solely by chance and is thus stochastic. Basically, gene drift is an important criterion for the emergence of new species. Particularly in populations of small size, random changes in allele frequency, as occurs with gene drift, have a strong effect on the evolution of individuals. If a small population is cut off from the population as a whole, that population will have only a slice of genes. However, the allele frequency present is crucial for the evolutionary development of the subpopulation. Within gene drift, there is also a special form: the bottleneck effect. In this effect, the size of the population is significantly reduced due to a random event. As a consequence, the genetic variability present in the population decreases. After the random event, the allele frequencies differ significantly from those of the original population in the majority of cases. The lower genetic diversity in the truncated population then makes adaptations to the environment more difficult and may present survival difficulties for the organisms. However, gene drift may also occur in larger populations that have divided into small subpopulations. The condition here is that genes change randomly and these changes are passed on to offspring.
Function and task
The importance of gene drift to humans lies primarily in the evolutionary developmental history of mankind. Gendrift represents an important factor in the formation and transmission of new genetic adaptations to the environment. Like selection, genetic variation and isolation, gene drift is also one of the so-called evolutionary factors. Thus, it plays a major role in the emergence and evolution of populations. Gendrift is a probability effect. Those genes that are inherited from one generation to the next do not represent an exact copy. Instead, the genes that are inherited are randomly selected. This effect is more noticeable the smaller the population size, because smaller populations have higher fluctuations in allele frequencies than larger populations. Gene drift acts simultaneously with natural selection. Both factors change the gene pool of a population. Changes in the composition and frequency of allele frequencies occur. As a consequence, the phenotypic characteristics of the individuals and thus of the population change. It should be noted here that gene drift occurs regardless of whether the results have a positive or negative effect on the survival and adaptability of the offspring. This is because gene drift is triggered by random events and thus occurs independently of genetic adaptation. On the other hand, natural selection strengthens those phenotypic traits that increase the genetic fitness of individuals and thus eventually populations. In populations with many members, natural selection usually exerts a greater influence on changing allele frequencies. The situation is different in numerically small populations, where in the vast majority of cases gene drift has a stronger effect.
Diseases and disorders
Gendrift may have a significant effect on human populations and has led to extinction of populations in some cases throughout evolutionary history.When a population undergoes a large reduction in numbers, which has occurred frequently during human evolution, gene drift in some cases causes drastic changes in allele frequency. These changes occur independently of natural selection. In the process, advantageous adaptations to the environment that have already been acquired may be lost. This is referred to as the bottleneck effect described above. The resulting disadvantages are partly relativized by the so-called purging. The founder effect plays a major role in nomadic populations, for example. If a small number of individuals founds a new population by splitting off from the initial population, this partly results in a contradiction to natural selection. This is especially true if the members of the newly founded population are characterized by rare gene frequencies. Due to the founder effect in gene drift, hereditary diseases can accumulate in human populations. If the frequency of specific genes changes in descendant generations, sometimes an allele is completely lost within a population. On the other hand, it can also become the only allele. Overall, this reduces genetic variability and the gene pool becomes smaller, which ultimately has a negative impact on survival.
