A mutation is called persistent changes in the genotype that occur due to the influence of external and internal factors. The ancestor of the term is Hugo de Vries - a Dutch botanist and geneticist. The process when mutations occur is called mutagenesis. In today's article, we will cover the topic of mutation and talk about the role of mutation in the evolutionary process.
Causes of the phenomenon
The mutation process is characterized by two qualities - spontaneity and induction. The appearance of a spontaneous mutation is characterized by spontaneity and occurs at any stage of the development of the organism. As for the environment, it must be natural.
The induced type of mutation is a hereditary change in the genome that occurs due to exposure to various mutagens. Organisms are placed either in artificially created (experimental) or in adverse environmental conditions.
Living cells perceive mutagenesis as a natural process for them. The main processes responsible for the mutation include: replication and impaired DNA repair, transcription process and genetic recombination.
Mutagenesis and its models
Special scientific approaches help to explain and understand the nature and mechanisms of the appearance of mutations. Polymerase changes are based on the theory of the direct and unique dependence of mutations with DNA polymer errors. In the tautomeric models of mutagenesis proposed by two well-known biologists, the idea was first raised that the main layer of mutations is the ability of DNA bases to be located in different tautomeric forms.
Early classification of mutations
Geneticist Meller created a classification of mutations based on the types of changes in the functioning of genes. As a result, the following species appeared:
- Amorphous. During mutation, the gene loses almost all of its functions. An example of a mutation is changes in Drosophila.
- Hypomorphic. Changed alleles continue to act according to the same scenario as wild ones. The synthesis of the protein product is carried out in smaller quantities.
- Antimorphic. Change in mutant trait. Some corn grains have become examples of mutations — they turn brown, not purple.
- Unmorphic.
Late classification of mutations
In modern scientific directories, there is a mention of a formal classification, which is based on changes in various structures. Based on this separation, the following mutations are distinguished:
- Genomic.
- Chromosomal
- Gene.
Changes in chromosomes are associated with genomic mutations, the total number of which does not correlate with the halide set.
Chromosomal mutations are credited with the rearrangement of individual chromosomes in large numbers. Genetic material in this case loses some part or, on the contrary, doubles it.
As for the gene mutation, it only slightly changes the DNA structure of the gene, unlike other species, but its occurrence occurs much more often.
Inside the gene species, another subspecies is called a point mutation. In it, one nitrogenous base is replaced by another.
The evolutionary role of mutation
It also happens that the harmfulness of mutations is gradually replaced by utility. The impetus for such changes is the ever-changing conditions for the existence of organisms. So what role do mutations play?
Take natural selection as an example - a well-known evolutionary process that is largely dependent on variability. Let us consider the evolutionary role of a mutation using the example of mutant melanists (individuals with a dark color), which were discovered by 14th-century English scientists when studying birch moths. In addition to butterflies painted in typically light colors, other individuals were found whose color was much darker. The reason for this strong difference was the mutated gene.
The fact is that the usual habitat for such butterflies are trees, on the trunks of which lichen grows abundantly. The industrial revolution that reigned in the early years, together with severe pollution of the atmospheric layers, led to the death of lichens. On once light trunks appeared soot, which interfered with the natural disguise of the birch moth. All this led to the fact that individuals whose habitats were industrial areas, changed the color of their morph from light to dark. This evolutionary role of the mutation has helped many butterflies survive, while their not very successful light relatives have been the victims of attacks by birds of prey.
Similar changes occur in a wide variety of species around the world. The appearance of such useful traits, which are the basis of the evolutionary role of mutations, leads to the fact that natural selection gives rise to new subspecies and species among living organisms. Mutation occurs constantly, because it is a natural ability of our genes.
You will find even more information about mutations in biology textbooks and specialized scientific literature.