Mutation is a stable transformation of the genotype, which takes place under the influence of the external or internal environment. The terminology was proposed by Hugo de Vries. The process by which this change occurs is called mutagenesis.
Later in the article we will consider in more detail the nature of this transformation, we will also find out what a somatic mutation is.
Terminology
Somatic mutation is a modification of a gene in certain cells during the individual development of an organism. Previously, it was believed that the transformation of the genotype usually occurs predominantly before the formation or in mature germ cells and necessarily at an embryonic level. This is the reason why gametic changes are recreated by all cells that are formed during the development of the zygote. And it appeared with the participation of the initial mutational gamete. To date, many facts indicate the occurrence of modifications of the genotype at any time of the individual development of the organism.
Changes in plants
Science has long proven that somatic mutation is quite common in plants. An examplecan serve as kidney variations, which were described in detail by Ch. Darwin. Such changes most often occur in fruit trees and ornamental plants and are used to develop new varieties of them. Different types of apples, oranges and various other fruits were obtained due to the discovery by man of certain branches that were different from the whole tree. This may be the speed of ripening, and the size, and shape, and the number of fruits.
Using vegetative shoots from such branches, you can get trees with identical features of the mother part. It is believed that they received their original origin from the transformation of the initial cell at the point of growth. Based on the fact that plants do not have an extremely isolated path at the embryonic level, the fact of sexual reproduction with vegetative mutations is confirmed. This is possible in the case when the transformation has penetrated into the subepidermal layer, since germ cells are formed from it. As a result, the same plant can contain both modified and non-mutated tissues that differ from each other.
Transformations in animals
Animals do not reproduce vegetatively and do not have an isolated rudimentary pathway. Therefore, the concept of "somatic mutation" in relation to them is used extremely rarely. Genetics is most studied in some forms, due to which these modifications can be observed. These include the Drosophila fly. The male, for example, hadsome parts of the body or organs were found different from the rest in color or shape.
Somatic mutations in humans
Changes occur in diploid cells. Therefore, modification is manifested only in the presence of dominant genes or recessive ones that are in a homozygous state. Somatic mutations in humans directly depend on the time of their occurrence. The earlier in the development of changes in genes, the more affected cells will suffer. In what case can somatic mutations be observed in humans? This has not been confirmed for sure. Perhaps this process is due to a change in the color of the iris, cancerous degeneration and others. On the other hand, the development of malignant tumors, for example, is mainly influenced by carcinogens, especially the negative ones - radiation and chemicals.
Chromosomal aberrations
This definition should be understood as a change in the structure of chromosomes. Somatic mutation also leads to this process. If a change in genes occurs at an early stage of development, bilateral mosaics may appear. They have one half of the body with dominant traits, and the other with recessive ones. In the case of the sex chromosome, gynandromorphs are formed that have female and male characteristics in half. A somatic mutation with a complete separation of the germline affects a certain part of the germ cells. As a result, this is observed in some offspring in the form of a rudimentary transformation. However, this phenomenon is very rare. ATin general, such a change in genes is not found in the offspring. As you know, spontaneous somatic mutation is also a rather rare phenomenon. According to the results of various experiments, it is enhanced by the same factors as the rudimentary, namely X-rays.
Mutability of genes causes many phenomena. In plants, for example, these include variegation, variegation, as well as a change in the color of other parts of the object in question. In humans, as mentioned above, the phenomena and results of somatic mutations have not been definitely proven. However, it can be assumed that these are manifestations of mosaic and asymmetrical features, such as different eye colors, their spotting, pigmentation, and others. At present, the opinion has spread that the consequences of somatic mutations are various kinds of malignant tumors. In addition, they are trying to find a connection with chromosomal aberration. Some believe that the main factor is an increase in the number of chromosomes, other researchers believe that the cause is their elimination. However, this is just guesswork. There is no scientific evidence for this, and cytological studies have not yet shown anything.
