The mutational process of evolution is one of the most important links in development. In most cases, it initially 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 mutation process in evolution.
General information
The mutational process is a hereditary sudden change provoked by a sharp functional and structural transformation of genetic material. The latter is organized into a hierarchy of various elements: from the molecular sites present inside the gene, to chromosomes and genomes. The mutation process is a pressure factor on the population. As a result of it, the frequency of one allele changes in relation to another.
Positive effect
Due to the presence of mutant alleles in the gene pool in the heterozygous genotype, the direct negative effect on the phenotypic expression of that trait that is controlled by this gene is excluded.
Due to hybrid power (heterosis), many mutations in the heterozygous state often contribute to an increase in the body's viability.
By preserving alleles that do not have adaptive value in the present environment of existence, but are able to acquire it either in the future or in the development of other ecological niches, a reserve of variability is formed.
The value of the mutation process
The importance is due to the fact that with the constant occurrence 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. The role of the mutation process is to increase genetic heterogeneity. However, without the participation of other factors, he is not able to direct the transformation of the natural population.
Mutation process is a source of elementary material, a reserve of variability. The appearance of transformations has a statistical and probabilistic character. The evolutionary significance of the process is to maintain a high heterogeneity of natural populations, to participate in the formation of various alleles and the emergence of new genes. The mutation process creates the full spectrum of variability of a particular gene pool. In its constant course, it has an undirected and random character.
Specificity
The mutation process occurs throughout the existence of a lifetime. Some transformations can occur repeatedly in various organisms. Gene pools are constantly influenced by the mutation process. This compensates for the high probability of loss of a single change in a number of generations. Despite the fact that the mutational 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 meaning of mutations. They penetrate into new genomes, appear in various genotypic environments. The potential number of such combinations of genetic material in any population is huge. However, only an insignificant part of the theoretically probable number of options is realized. The implemented share of combinations determines the uniqueness of almost every individual. This factor is extremely important for the implementation of natural selection.
Features of manifestation
Mutations are an elementary material of evolution. There are several types: genomic, chromosomal, gene. Among the features of the manifestation of mutations, their expressivity should be highlighted. It reflects the degree of their phenotypic expression. In addition, penetrance is characteristic of mutations. It represents the frequency of phenotypic manifestations in one allele of a particular gene in a population, regardless of expressivity.
Gene mutations
They represent a transformation of the nucleotide sequence. The mutation process in this case changes the nature of the gene. Usually there is a molecular transformation causing a phenotypic effect. Suppose that in a particular gene at a particular point in the codes there is a CTT encoding glutamic acid. When replacing only one nucleotide, it can turn into a GTT codon. He will participate in the synthesis of not glutamic acid, but glutamine. The initial and mutant protein molecules are different, and this is likely to result in secondary phenotypic differences. Exact replication of the new allele will occur until a new change occurs. With a gene mutation, a series or pair of homologous elements thus appears. You can make a reverse conclusion. The presence of allelic variation in a given gene means that it mutated at a certain time.
Additionally
Heterozygous state, diploid genotype, "silent DNA" - all these are traps for mutations. With the degeneracy of the genetic code, the rarity of the occurrence of transformations speaks of repair. Mutation processes must occur in existing living organisms with a certain frequency. It should be sufficient to cause changes through which populations would be brought to a new level. Mutations are found in various concentrations. Some of them should participate in the historical development of living organisms, contributing to the formation of new taxa. Mutations, as a rule, appear without transitions, discrete and spasmodic. The change that once appeared is steady. It is transmitted to posterity. Mutations do not occur directionally. One and the same change can be repeated more than once.
Adaptive value
Most of the new mutants have significantly lower viability than the wild / normal type. At the same time, it is expressed in various degrees: from a subvital barely noticeable to a semi-lethal and lethal state. When analyzing the viability of the Drosophila fly mutants that appeared during changes in the X chromosome, it was lower in 90% of individuals than in normal ones. In 10%, a supervital state was noted - increased vitality. In general, the adaptive value of the appeared mutants is usually reduced. It is characterized by the functional usefulness of morphological characters and fecundity, physiological viability.