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

BIOLOGY

SECTION 1. BIOLOGICAL BASES OF HUMAN VITAL ACTIVITY

1.3. MOLECULAR-GENETIC AND CELLULAR LEVELS OF LIFE ORGANIZATION

1.3.3. Hereditary apparatus of eukaryotic cells and its functioning - molecular level

Molecular Organization of the eukaryotic genome

It is characterized by an excess amount of DNA and the presence of sequences with varying degrees of repetitiveness. Excess DNA is found in varying amounts in almost all eukaryotic species. Prokaryotes lack it. The Human Genome size (DNA) is 3.5x109 nucleotide pairs, which is sufficient to form about 1.5 million genes. However, according to expert estimates, the human genome contains only 35 thousand genes. This means that the majority of nuclear DNA is not translated into an Amino Acid Sequence. According to modern data, only 2-3% of human Cell DNA contains information for coding the body's Proteins.

Unique and repetitive DNA nucleotide sequences are distinguished in the eukaryotic genome. Unique sequences are represented in The Genome by a single copy. They constitute the bulk of the genes and occupy half of the human genome. Repetitive sequences are represented by copies (from 2 to 107). Moderately repetitive and highly repetitive sequences are distinguished. Moderately repetitive sequences have no more than 106 copies, alternate with unique nucleotide sequences, and are characterized by the presence of inverted repeats (palindromes). Highly repetitive sequences are short segments ranging from 5 to 500 nucleotide pairs in length, arranged one after another (in tandem). Such sequences form clusters containing up to 10 million copies and make up the satellite DNA fraction. This fraction is localized in constitutive Chromatin regions, predominantly pericentromeric and telomeric, is genetically inert (not transcribed), and accounts for 12% of the human genome.



Last update: 08/08/2026

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