The section of DNA where a certain gene is located is called a locus. It may contain alternative variants of genetic information - alleles. In any population there are a large number of these structures. In this case, the proportion of a particular allele in the total genome of a population is called the frequency of the gene.
For a certain mutation to lead to evolutionary changes in species, its frequency must be high enough, and the mutant allele must be fixed in all individuals of each generation. With a small amount of it, mutational changes are not able to affect the evolutionary history of organisms.
In order for the allele frequency to increase, certain factors must act - genetic drift, migration and natural selection.
Gene drift is the random growth of an allele under the influence of several events that are combined and have a stochastic character. This process is associated with the fact that not all individuals in the population take part in reproduction. It is most characteristic of traits or diseases that are rare, but due to the lack of selection, are able to be stored in a genus or even an entire population of a small size forlong time. This pattern is often observed in a small population, the number of which does not exceed 1000 individuals, since in this case migration is extremely small.
In order to better understand genetic drift, the following patterns should be known. In cases where the allele frequency is 0, it does not change in subsequent generations. If it reaches 1, then the gene is said to be fixed in the population. Random gene drift is a consequence of the fixation process with the simultaneous loss of one allele. Most often, this pattern is observed when mutations and migrations do not cause permanent changes in the constituent loci.
Because gene frequency is non-directional, it reduces species diversity and also increases differences between local populations. It is worth noting that this is counteracted by migration, in which different groups of organisms exchange their alleles. It should also be said that genetic drift has practically no effect on the frequency of individual genes in large populations, but in small groups it can become a decisive evolutionary factor. In this case, the number of alleles changes dramatically. Some genes can be irretrievably lost, greatly impoverishing genetic diversity.
As an example, we can cite mass epidemics, after which the restoration of the population was carried out practically at the expense of a few of its representatives. Moreover, all descendants had the same genome as their ancestors. Further expansionallelic diversity was ensured by the importation of producers or outbound matings, which contribute to the growth of differences at the gene level.
The extreme manifestation of genetic drift can be called the emergence of a completely new population, which is formed from only a few individuals - the so-called founder effect.
It should be said that the patterns of genome rearrangement are studied by biotechnology. Genetic engineering is a technique of this science that allows you to transfer hereditary information. At the same time, gene transfer allows you to deal with the interspecies barrier, as well as give organisms the necessary properties.
