Genetics is the science of heredity and variability of organisms. In the basis of genetics are the laws of inheritance, according to which all basic features and properties of the body are determined by separate hereditary factors, localized in the specific structures cell chromosomes (see). Direct carriers of genetic information are molecules of nucleic acids (see) - deoxyribonucleic (DNA) and ribonucleic (RNA).
Genetics studies the nature of the material carriers of heredity, possible ways and methods of artificial synthesis, mechanisms of action, changes and reproduction, control these functions, forming a complex of properties and characteristics of the entire organism, the relationship of heredity, variability, selection and evolution.
The main method of research in genetics is a genetic analysis which is carried out at all levels of organization of living matter - molecular, chromosomal, cellular, organism, population, and depending on the purpose of the study is divided into a number of private methods - hybridological, population, mutation, recombination, cytogenetic and other
Hybridological method through a series of crosses (direct or return) allows you to set the patterns of the inheritance of individual characteristics and properties of the organism. The laws of inheritance at the level of the population are defined using population-based analysis. Both method often include elements of mathematical statistics.
Through mutation and recombination techniques is carried out the analysis of structure of material carriers of heredity, their changes, mechanisms of operation and the exchange of genes at crossing and a number of other issues. Cytogenetic method combined the principles of cytological and genetic analyses provide insights about the anatomy material carriers of heredity. Genetics uses cytochemical, biophysical, electronomicroscopic and other research methods.
Depending on the object and method of research in genetics has raised a number of separate areas: molecular genetics, biochemical genetics, medical genetics, population genetics, radiation genetics, genetics of microorganisms, animals, plants, cytogenetics, and other immunogenetic
Medical genetics studies the regularities of pathological heredity of human rights. Despite some overlap areas of research, medical genetics should be distinguished from anthropology that deals with the study of inheritance normal variations of structure and morphological features of the man.
Medical genetics integrates the principles and methods of genetics and medicine. Its subject is the relationship of heredity and disease due to various violations of material carriers of heredity - chromosomes and genes. Such changes can be gene mutations, deletions, translocation, the chromosomes nondisjunction and others (see Variability).
In the research area of medical genetics includes patterns of transmission of pathological traits to offspring, the questions of etiology, pathogenesis and prevention of hereditary diseases, questions of causality pathological variability of man. Medical genetics studies also genetically determined predisposition to diseases, occurrence, development and severity depends on the environmental conditions (hypertension, diabetes, and others), genetically determined resistance to certain diseases (resistance to malaria and others).
Medical genetics uses a number of special methods of research: genealogical analysis inheritance pathology)pedigree, twin (analysis and comparison of development twins depending on habitat conditions), population statistics (distribution trait within a population) and some other
The main task of medical genetics is the reduction in the number of hereditary diseases, which are achieved through an early warning of developing certain hereditary disease phenylketonuria, galactosemia , and others), detection of hidden media pathological symptom, identification of genetic risk for some of the environmental factors (radiation, chemical and physical factors) and elimination of their influence.
In its time the Soviet Union had created a network of medical-genetic consultations, where medical geneticists could give qualified advice on the forecast of morbidity in families with congenital malformations and hereditary diseases, as well as to facilitate early identification of carriers of the abnormal genes among the population.
Cm. also Heredity.

Genetics of microorganisms genetics section studying variation and heredity of microorganisms. This includes genetics of bacteria, genetics of viruses, genetics of fungi and other
Genetics of microorganisms studying inherited modify the properties of microbes that occur spontaneously (spontaneous mutation) or as a result of various chemical and physical effects (induced mutations), and the processes of exchange of genetic material between organisms, structure . and the function of their genetic apparatus.
The exchange of genetic material of the bacteria are carried in three different ways: 1) transformation of bacteria; while in the bacteria-recipient is made part of the genes of a bacterium donor in the form of isolated molecule of DNA; 2) transduction of bacteria; in this case the role of the carrier of genetic material between cells of the donor and recipient perform moderate bacteriophages. In the first and second methods do not require direct contact between donor and recipient; 3) algae bacteria; the exchange of genetic material occurs at the moment of direct contact between donor and recipient. After hitting the genetic material of the donor in the bacteria-recipient is the actual genetic exchange: recombination between DNA molecules. Genetic exchange of viruses is co multiplication of two or more virus particles inside one cell.
The success of modern genetics of microorganisms is possible to explain a number of phenomena and processes important for practice. Clarify the mechanisms of formation of bacterial drug resistance, and the ways of its solution. The resulting mutants - active producers of antibiotics, vitamins and amino acids, which are important for medical and economic practice.
Radiation genetics - genetics section, devoted to the action of radiation on hereditary structures. As a result of exposure to ionizing radiation or UV rays in the chromosomes occur mutational changes, manifested in the structural rearrangements of chromosomes and in point mutations that alter the functionality of genes. Mutation rate depends on the dose of radiation, and exposure conditions; for example, the presence in the environment of oxygen dramatically increases the biological efficiency of x-rays. Radiation mutations arise as a result of defeat of chromosomal DNA directly by getting into the chromosomes of energy quanta, and through the formation of various active ingredients in the cell.
Mutations occur in somatic cells, can cause changes in the irradiated organism to cause leukemia, malignant tumors, to speed up the process of aging, and cause temporary or permanent sterility. Mutations in germ cells may appear in the form of hereditary anomalies in subsequent generations of organisms.
Protection of heredity person from the damaging effects of radiation is the most important practical task of radiation genetics. Currently, there are a number of chemical compounds that can significantly weaken the mutagenic effect of radiation at introduction before or after exposure.
In recent years found that the cells of humans and animals, there are special enzyme systems that can clear up some of the damage hereditary structures, caused by ionizing radiation and ultraviolet light.