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 for the corresponding locus. Consider further the role of the mutation process in evolution.
General information
Mutation 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 molecular sites present within a gene to chromosomes and genomes. The mutation process is a factor of pressure on the population. As a result, the frequency of one allele changes in relation to another.
Best effect
Due to the presence of mutant alleles in the gene pool in the heterozygous genotype, a direct negative impact on the phenotypic expression of the trait controlled by this gene is excluded.
Due to hybrid power (heterosis), manymutations in the heterozygous state often contribute to an increase in the viability of the organism.
Through the preservation of alleles that do not have adaptive value in the present environment of existence, but are able to acquire it either in the future or when developing other ecological niches, a reserve of variability is formed.
The meaning 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. At the same time, without the participation of other factors, it is not able to direct the transformation of the natural population.
Mutational 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 lies in maintaining the high heterogeneity of natural populations, participating in the formation of various alleles and the emergence of new genes. The mutation process creates a full range of variability in a particular gene pool. With its constant flow, it has an undirected and random character.
Specifics
The mutation process occurs throughout the existence of all life. Some transformations can occur repeatedly in different organisms. Gene pools are under constant influencemutation process. This compensates for the high probability of loss of a single change in a number of generations. Despite the fact that the mutation process exerts relatively little pressure on a single gene, with a large number of them, the genetic structure undergoes significant changes.
Mechanism and result
As a result of continuous crosses, many combinations of alleles appear. Genetic combinatorics repeatedly examines the significance of mutations. They penetrate into new genomes, appear in different genotypic environments. The potential number of such combinations of genetic material within any population is enormous. However, only an insignificant part of the theoretically probable number of options is realized. The realized proportion 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 the elemental stuff of evolution. There are several types: genomic, chromosomal, gene. Among the features of the manifestation of mutations, one should highlight their expressivity. It reflects the degree of their phenotypic expression. In addition, mutations are characterized by penetrance. It represents the frequency of phenotypic manifestations in a single 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 action of the gene. Usually there is a molecular transformation that causes a phenotypic effect. Suppose that in a certain gene, at a certain 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 original and mutant protein molecules are different, and this is likely to lead to secondary differences of a phenotypic nature. 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 arises. You can also draw the opposite conclusion. The presence of allelic variability for a particular gene means that it was mutated at a certain time.
Extra
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 reparation. Mutation processes should occur in existing living organisms with a certain frequency. It should be sufficient to cause changes by which populations would be brought to a new level. Mutations are found at 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 andspasmodically. Once a change occurs, it is stable. It is passed on to offspring. Mutations do not occur in a directed way. The same change can be repeated over and over again.
Adaptive Value
Most of the new mutants have significantly lower viability than the wild/normal type. At the same time, it is expressed in varying degrees: from a subvital, barely noticeable to a semi-lethal and lethal state. In the analysis of the viability of Drosophila mutants that appeared with changes in the X chromosome, in 90% of individuals it was lower than in normal ones. 10% had a supervital state - increased vitality. On the whole, the adaptive value of the emerging mutants is, as a rule, lowered. It is characterized by the functional usefulness of morphological features and fertility, physiological vitality.
