Education, The science
Mutational process as a factor of evolution
The mutational process of evolution is one of the most important links in development. In most cases, initially it has an adverse effect on the phenotype of individuals. However, being recessive, altered alleles are present, as a rule, in gene pools in heterozygous genotypes at the corresponding locus. Let us further consider the role of the mutational process in evolution.
The mutational process is a hereditary sudden change, provoked by a sharp functional and structural transformation of the genetic material. The latter is organized into a hierarchy of various elements: from the molecular sites present within the gene, to the chromosomes and genomes. The mutational process is a factor of pressure on the population. As a consequence, the frequency of one allele changes with respect to the other.
Due to the presence of mutant alleles in the gene pool in the heterozygous genotype, a direct negative effect on the phenotypic expression of the trait that is controlled by this gene is excluded.
Due to the hybrid capacity (heterosis), many mutations in the heterozygous state often contribute to an increase in the viability of the organism.
By preserving alleles that do not possess adaptive value in the real environment of existence, but are able to acquire it either in the future or in the development of other ecological niches, a reserve of volatility is formed.
The significance of the mutation process
The importance is due to the fact that with the constant emergence of spontaneous changes and their combinations, new combinations of genes and transformations arise when crossing. This, in turn, inevitably leads to hereditary adjustments in the population. мутационного процесса состоит в повышении генетической гетерогенности. The role of the mutational process is to increase genetic heterogeneity. At the same time, without the participation of other factors, he is unable to direct the transformation of the natural population.
элементарного материала, резерва изменчивости. The mutational process is the source of the elementary material, the reserve of variability. The appearance of transformations has a statistical and probabilistic character. The evolutionary value of the process is to maintain high heterogeneity of natural populations, to participate in the formation of various alleles and the emergence of new genes. The mutational process creates a full range of variability of a particular gene pool. With his constant flow, he has an undirected and random character.
происходит на протяжении существования всей жизни. The mutational process occurs throughout the lifetime of the whole life. Some transformations can occur many times in different organisms. Genofunds are under the constant influence of the mutational process. This compensates for the high probability of a single change in the number of generations. оказывает относительно небольшое давление на отдельно взятый ген, при большом количестве последних генетическая структура подвергается существенным изменениям. Although the mutation process exerts relatively little pressure on a single gene, with a large number of the latter, the genetic structure undergoes significant changes.
Mechanism and result
As a result of continuous crosses, many combinations of alleles appear. Genetic combinatorics repeatedly explores the significance of mutations. They penetrate into new genomes, appear in various genotypic environments. The potential number of such combinations of genetic material within any population is enormous. However, only a negligible fraction of the theoretically probable number of variants is realized. The uniqueness of almost every individual is determined by the proportion of combinations implemented. This factor is extremely important for the implementation of natural selection.
Features of manifestation
Mutations are the elementary material of evolution. There are several of their types: genomic, chromosomal, gene. Among the features of the manifestation of mutations should be highlighted their expressiveness. It reflects the degree of their phenotypic severity. In addition, mutations are characterized by penetrance. It is the frequency of phenotypic manifestations in one allele of a particular gene in a population, regardless of expressiveness.
They represent the transformation of the nucleotide sequence. The mutational process in this case changes the nature of the action of the gene. Usually there is a molecular transformation that causes a phenotypic effect. Suppose that in a particular gene at a particular point in the codes there is a CTT coding for glutamic acid. When replacing only one nucleotide, it can become a GTT codon. He will participate in the synthesis of non-glutamic acid, and glutamine. The initial and mutant protein molecules are different, and probably this will lead to secondary phenotypic differences. Exact replication of the new allele will occur until a new change occurs. In the case of a gene mutation, a series or pair of homologous elements thus occurs. You can do the opposite. The presence of allelic variability for a particular gene means that it was mutated at a certain time.
Heterozygous condition, diploid genotype, "silent DNA" are all traps for mutations. With the degeneracy of the genetic code, the rarity of the appearance of transformations is indicative of reparation. Mutational processes must occur in existing living organisms with a certain frequency. It should be sufficient to induce changes through which populations are brought to a new level. Mutations are found in various concentrations. Some of them should participate in the historical process of development of living organisms, contributing to the formation of new taxa. Mutations, as a rule, appear without transitions, discretely and spasmodically. The change that appeared once is stable. It is passed on to the descendants. Mutations arise not directed. The same change can be repeated many times.
Most of the new mutants have a significantly lower viability than the wild / normal type. In this case, it is expressed in varying degrees: from the subvital to subtle to semi-lethal and lethal state. When analyzing the viability of mutants, the fly flies that appeared with changes in the X chromosome, in 90% of the individuals it was lower than in the normal ones. In 10% there was a supernital condition - increased viability. In general, the adaptive value of the mutants that appeared is, as a rule, lowered. It is characterized by the functional usefulness of morphological features and fertility, physiological viability.