MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Y.I. Fedoniuk 2010

BIOLOGY

SECTION 1. BIOLOGICAL BASES OF HUMAN VITAL ACTIVITY

1.4. ONTOGENETIC LEVEL OF LIFE ORGANIZATION

1.4.2. Fundamentals of Human Genetics

Somatic and Germline Mutations, Mosaicism

Mutations occur in the Cells of any Tissues of a multicellular Organism and at various stages of its development. Depending on The Cell type, mutations are subdivided into somatic and germline. Somatic mutations are those occurring in somatic (non-germ) cells. Their mechanism of origin is associated with mitotic disturbances. Gene, chromosomal, and genomic somatic mutations are distinguished. The Phenotypic effect of a somatic mutation depends on the organism's age: the earlier it occurs, the more severe the potential damage. In some cases, cells with an increased rate of growth and division are formed. These cells can initiate tumors—either benign, which do not significantly affect the entire organism, or malignant, leading to neoplastic diseases.

Somatic mutations are not inherited during sexual reproduction, but they are transmitted during vegetative propagation—specifically, to those cells that originate via mitosis from the mutant cell. Somatic mutations utilized in vegetative propagation are applied in plant breeding. For instance, I.V. Michurin developed the Antonovka 600-gram apple cultivar using this approach.

Somatic mutations frequently lead to mosaicism. Mosaicism is the presence of genetically distinct cell lines within an individual, referred to as a mosaic. In mosaics, only the body part that developed from the division of the mutant cell is altered. Individuals with eyes of different colors are an example of human mosaics. Mosaicism also occurs in Down syndrome, where a subset of cells possesses a normal karyotype (46) while another subset exhibits an abnormal one (47).

Germline (gametic) mutations arise in Gametes or in the precursor cells from which they develop. Their primary mechanism of origin involves meiotic disturbances. Germline mutations are inherited through sexual reproduction. Dominant mutations manifest themselves as early as the first generation. Recessive mutations do not appear in the first generation because they remain in a heterozygous state (Aa); however, they may manifest In the second and subsequent generations once they transition to a homozygous state (aa).