The portion of DNA that hosts a particular gene is called a locus. It may contain alternative variants of genetic information - alleles. In any population there are a large number of these structures. The share of a particular allele in the general genome of a population is called the frequency of the gene.
In order for a particular mutation to lead to evolutionary changes in species, its frequency must be sufficiently high, and the mutant allele must be fixed in all individuals of each generation. With its insignificant amount, mutational changes are not able to affect the evolutionary history of organisms.
In order for the allele frequency to grow, certain factors must act - gene drift, migration, and natural selection.
Gene drift is a random allele growth due to several events that combine and have a stochastic character. This process is associated with the fact that not all individuals in the population participate in reproduction. It is most characteristic of signs or diseases that are rare, but due to the lack of selection they can be stored in the genus or even a whole population of a small size for a long 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 the drift of genes, you should know the following patterns. In cases where the frequency of the allele is 0, in subsequent generations it does not change. If it reaches 1, then they say that the gene in the population is fixed. The random drift of genes 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 a constant change in the constituent loci.
Since the frequency of genes is non-directional, it reduces the diversity of species and also increases the differences between local populations. It is worth noting that this is counteracted by migration, in which different groups of organisms exchange their alleles. It must also be said that gene drift practically does not affect the frequency of individual genes in large populations, but in
small groups it can become a decisive
evolutionary factor. The number of alleles changes dramatically. Some genes can be irretrievably lost, which significantly impoverishes genetic diversity.
As an example, mass epidemics can be cited, after which the restoration of the population was carried out at the expense of several of its representatives. Moreover, all descendants had a gene identical to their ancestors. In the future, the expansion of allelic diversity was ensured by the importation of producers or exit mating, which contribute to the growth of differences at the gene level.
The extreme manifestation of gene drift can be called the emergence of a completely new population, which is formed only from a few individuals - the so-called founder effect.
It should be said that the laws of genome rearrangement are being studied by biotechnology. Genetic engineering is the technique of this science, which allows the transfer of hereditary information. In this case, gene transfer allows you to deal with the interspecific barrier, as well as give the necessary properties to organisms.