Genome organization and three kinds of heritable changes: general description and stochastic factors (a review).

Due to the increased knowledge of genome architecture, topology, and the mechanisms of hereditary variability, the list of genetic components has grown. This review outlines the general features and principles of genome organization in diverse organisms. The genome codes, stores, and transfers information in both structurally and dynamically. The genome includes two subsystems of genetic elements: obligatory (genes and gene families) and various types of facultative elements which are predominant the content of the human genome. The features of three kinds of heritable changes: mutations, variations (changes in the number or topography of facultative elements), and epigenetic alterations are described. Facultative elements are the first to react to environmental challenges. Together with epigenetic changes, they implement the operational genomic memory. This review discusses both the role of stochastic factors and the transient features of DNA components.