Mutation (From the Latin word "mutatio" is a change) is a persistent change in the genotype that has occurred under the influence of internal or external factors. Distinguish between chromosomal, gene and genomic mutations.
What are the causes of the mutations?
- Unfavorable environmental conditions, conditions created experimentally. Such mutations are called induced.
- Some processes occurring in the living cell of the body. For example: violation of DNA repair, DNA replication, genetic recombination.
Mutagens are factors that cause mutations. Are divided into:
- Physical - decay radioactive, radiation ionizing and ultraviolet, too high temperature or too low.
- Chemical - reducing agents and oxidizers, alkaloids, alkylating agents, nitro derivatives of urea, pesticides, organic solvents, some medicines.
- Biological - some viruses, metabolic products (metabolism), antigens of various microorganisms.
Main properties of mutations
- Passed by inheritance.
- Caused by a variety of internal and external factors.
- Appear abruptly and suddenly, sometimes repeatedly.
- Can mutate any gene.
What are they like?
- Genomic mutations are changes that are characterized by the loss or addition of one chromosome (or several) or a complete haploid set. There are two types of such mutations - polyploidy and heteroploidy.
Polyploidy is a change in the number of chromosomes, which 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, which is a multiple of the halogen set. As a result of this mutation, individuals with an anomalous number of chromosomes - polysomics and monosomics appear on the light. About 20-30 percent of monosomies die in the first days of intrauterine development. Among the individuals born there are individuals with the Shereshevsky-Turner syndrome. Genomic mutations in the plant and animal world are also diverse.
- Chromosomal mutations are changes that occur when the chromosome structure is rearranged. In this case, the transfer, loss or duplication 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 are observed. In rare cases, Robertson's 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 inversion or duplication of different parts of the gene. Effects of mutations of the gene type are diverse. Most of them are recessive, that is, they do not manifest themselves in any way.
Also mutations are divided into somatic and generative
- Somatic mutations are changes in any cells of the body, except gametes. For example, when a plant cell mutates, from which the kidney subsequently develops, and then the escape, all its cells will be mutant. So, on a bush of a red currant the branch with black or white berries can arise.
- Generative mutations are changes in the primary sex cells or gametes that have formed from them. Their properties are passed on to the next generation.
By the nature of the impact on the living organism mutations are:
- Fatal - owners of such changes die either in the stage of embryonic development, or in a short enough time after birth. This is almost all genomic mutations.
- Semilattice (for example, hemophilia) - characterized by a sharp deterioration in the performance of any system in the body. In most cases, half-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. Fixing these signs can lead to the formation of a new subspecies or species.