Gene mutations - this is the reason why the formation of a group of diseases that is heterogeneous in clinical manifestations, which is called "gene diseases". The total frequency of their occurrence in the human population is from two to four percent.
Change (mutation) of genes is a factor provoking the development of many forms of hereditary diseases . In modern medicine, more than three thousand such pathologies are described. The most common manifestation of the disease is fermentopathy. It is believed that gene mutations can affect embryonic, transport, and structural proteins. Pathological changes can be realized at different periods of ontogenesis (development). Most of them are characteristic of the intrauterine (up to 25% of all hereditary pathologies) and pre-puberty (before puberty) period (about 45%). Gene mutations occur in puberty (puberty) and adolescence (about 25%). A relatively small number (about 10%) of pathological changes are detected over twenty years.
Hereditary diseases are classified according to the type of inheritance (autosomal recessive, autosomal dominant and others), depending on the organ or system that is more involved in the pathological process (endocrine, neuromuscular, ocular and others), taking into account the nature of the metabolic defect (associated with a disorder of carbohydrate, mineral lipid metabolism, etc.). An independent group includes diseases that arise against the background of incompatibility of the fetus and mother by antigens in blood groups.
Provoked by gametic mutations, pathologies are inherited in accordance with the laws of Mendel. Perhaps the emergence of new or the development of changes inherited from past generations. In such cases, pathological structures are distributed into all cells of the body.
Gene mutations can occur in one of the cells at different stages of zygote fragmentation. In such cases, the body becomes mosaic in this structure. In other words, a normal allele (gene form) functions in some cells, and a mutant function in others. The dominance of the mutation is manifested phenotypically (by clinical signs) in the corresponding cells and provokes the development of the disease. In this case, there is a sufficient probability of a less severe degree of pathology, in contrast to full mutants.
Specialists classify changes of a functional and structural nature.
Structural gene mutations are subdivided into a transition — replacing one purine base (natural organic compounds, purine derivatives) with another, or one pyrimidine base (organic compounds - pyrimidine derivatives) with another pyrimidine base; in this case, the codon (unit of the genetic code) changes only the one in which the replacement occurred. There is also such a thing as “transversion”. In this case, there is a substitution of pyrimidine bases with purine or vice versa. In this case, the codon in which the replacement occurred also changes. In addition, there is a mutation by shifting the reading frame. In this case, a prolapse (deletion) or insertion (insertion) of several or one pair of nucleotides occurs. In accordance with the dropout or insertion area, more or fewer codons can be changed.
Mutations in functional genes are a change in the non-transcribed (coding) part in a DNA molecule. This provokes a disorder in the regulation of the functioning of structural elements. As a result, the synthesis rate of the corresponding protein can be increased or decreased to varying degrees.