Mutation (from the Latin word "mutatio" - change) is a persistent change in the genotype that has occurred under the influence of internal or external factors. There are chromosomal, gene, and genomic mutations.
What are the causes of mutations?
- Adverse environmental conditions, conditions created experimentally. Such mutations are called induced.
- Some processes occurring in a living cell of the body. For example: impaired DNA repair, DNA replication, genetic recombination.
Mutagens are factors that cause mutations. Are divided into:
- Physical - radioactive decay, ionizing and ultraviolet radiation, too high a temperature or too low.
- Chemical - reducing agents and oxidizing agents, alkaloids, alkylating agents, nitro derivatives of urea, pesticides, organic solvents, some medicines.
- Biological - some viruses, metabolic products (metabolism), antigens of various microorganisms.
The main properties of mutations
- They are inherited.
- Caused by a variety of internal and external factors.
- They occur spasmodically and suddenly, sometimes repeatedly.
- Any gene can mutate.
What are they like?
- Genomic mutations are changes that are characterized by the loss or addition of one chromosome (or several) or the complete haploid set. There are two types of such mutations - polyploidy and heteroploidy.
Polyploidy is a change in the number of chromosomes that is a multiple of the haploid set. Very rare in animals. In humans, two types of polyploidy are possible: triploidy and tetraploidy. Children born with such mutations usually live no more than a month, and more often die in the stage of embryonic development.
Heteroploidy (or aneuploidy) is a change in the number of chromosomes that is a multiple of the halide set. As a result of this mutation, individuals with an abnormal number of chromosomes — polysomics and monosomics — are born. About 20-30 percent of monosomics die in the first days of fetal development. Among those born, individuals with Shereshevsky-Turner syndrome are found. Genomic mutations in the plant and animal world are also diverse.
- Chromosomal mutations are those changes that occur during the restructuring of the chromosome structure. In this case, there is a transfer, loss or doubling of a part of the genetic material of several chromosomes or one, as well as a change in the orientation of the chromosome segments in individual chromosomes. In rare cases, Robertson translocation, that is, the union of chromosomes, is possible.
- Gene mutations. As a result of such mutations, insertions, deletions or substitutions of several or one nucleotides occur, as well as the inversion or duplication of different parts of the gene. The effects of gene mutations are diverse. Most of them are recessive, that is, they do not appear in any way.
Mutations are also divided into somatic and generative
- Somatic mutations are changes in any body cells other than gametes. For example, with a mutation of a plant cell from which a kidney and subsequently an shoot should later develop, all of its cells will be mutant. So, on a bush of red currant, a branch with black or white berries may appear.
- Generative mutations are changes in the primary germ cells or in the gametes that formed from them. Their properties are passed on to the next generation.
According to the nature of the effect on a living organism, mutations are:
- Lethal - the owners of such changes die either at the stage of embryonic development, or a fairly short time after birth. These are almost all genomic mutations.
- Semi-lethal (for example, hemophilia) - are characterized by a sharp deterioration in the functioning of any systems in the body. In most cases, semi-lethal mutations also soon lead to death.
- Useful mutations are the basis of evolution, they lead to the appearance of signs needed by the body. Being fixed, these signs can cause the formation of a new subspecies or species.