chromatinovým

Chromatin is the complex of DNA and proteins that forms chromosomes within the nucleus of eukaryotic cells. The primary proteins in chromatin are histones, which are responsible for packaging the vast amount of DNA into a compact structure. DNA is a negatively charged molecule due to its phosphate backbone, while histones are positively charged due to their abundance of basic amino acids. This electrostatic attraction allows DNA to wrap around histone proteins, forming nucleosomes, the fundamental repeating units of chromatin. Each nucleosome consists of approximately 147 base pairs of DNA wrapped around a core of eight histone proteins (two each of H2A, H2B, H3, and H4).

These nucleosomes are then further organized into a more condensed structure. The linker DNA between nucleosomes and another histone, H1, helps to facilitate this higher-order packing, leading to the formation of 30-nanometer chromatin fibers. Further coiling and folding of these fibers result in the highly condensed chromosomes observed during cell division. The structure of chromatin is not static; it is dynamic and can undergo modifications that influence gene expression. These modifications, such as acetylation, methylation, and phosphorylation of histones, can alter the accessibility of DNA to transcription machinery, thereby regulating whether genes are turned on or off. This dynamic regulation is crucial for cellular function and development.