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Variability of organisms - one of the most important manifestations of life. In the nature there are no two absolutely similar individuals. Distinctions are caused by hereditary and external factors. Therefore variability of organisms is expressed in two forms: hereditary and modification.

Mutations appear in cells of any fabrics of a metaphyte. If they arose in gametes, them call generative, in cells of other tissues of body somatic. The value of a mutation is various, it is caused by type of reproduction of an organism. Generative mutations are shown at germs of the next generation, and somatic - only at that individual at whom they arose, and to other generation are not descended.

It is accepted to refer any genetic transformations connected with a kernel and cytoplasm of a cage to mutations. Chemical changes of a gene, small and large reorganizations of chromosomes, change of number of chromosomes, and also changes of organellas of cytoplasm can be the cause of a mutation. From here name of different types of mutations. Gene or tochkovy mutations affect changes of molecular structure of a molecule of DNA. There is a replacement or inclusion of one couple nitrogenous bases, and also loss of several of their couples. Result of action of gene mutations - formation of protein of new type or lack of protein because of an obstacle of its synthesis. The mutations connected with gaps and reorganizations of chromosomes call chromosomal.

The modern genetics develops comprehensively. In it there are a lot of directions. Allocate genetics of microorganisms, plants, animals and the person. The genetics is closely connected with other biological sciences - theory of evolution, molecular biology, biochemistry. It is a theoretical basis of selection. On the basis of genetic researches methods of receiving hybrids of corn, sunflower, sugar beet, a cucumber, and also hybrids and hybrids of the animals possessing owing to a geterozis (geterozis-this acceleration of growth, increase in the sizes, increase of viability and efficiency of hybrids of the first generation in comparison with parental organisms) the increased efficiency were developed.

Kind of somatic mutations at plants – the pochkovy mutations appearing in meristemny cages of a point of growth of a stalk. The escape which developed from this cage completely has a mutant sign. Earlier these mutations called sportam. From such sport found in a grade of an apple-tree of Antonovk white I.V. Michurin received a known grade of Antonovk six hundred-gram. Many best American grades of an apple-tree were also created by use of pochkovy mutations. A number of valuable grades of potatoes also comes from spontaneously arisen forms with somatic mutations.

Later it was proved that chromosomes consist of protein and molecules of deoxyribonucleic acid (DNA). In DNA molecules hereditary information, the program of synthesis of the proteins which are a life basis on Earth is also put.