nukleosomy

Nukleosomy, also known as nucleosome, is the fundamental structural unit of chromatin in eukaryotic cells. It consists of a segment of DNA wrapped around a core of histone proteins. This packaging mechanism allows the long DNA molecules to be efficiently organized within the cell nucleus and plays a crucial role in regulating gene expression and DNA replication.

A nucleosome is composed of DNA wrapped approximately 1.65 times around a histone octamer, which includes two copies each of histones H2A, H2B, H3, and H4. The DNA-histone complex forms a bead-like structure, with the nucleosome core serving as the bead and linker DNA connecting neighboring nucleosomes. The length of DNA associated with each nucleosome is about 147 base pairs.

Nucleosomes are further organized into higher-order chromatin structures, such as chromatin fibers and loops, which facilitate the compaction of DNA into the confined space of the cell nucleus. The positioning of nucleosomes influences the accessibility of DNA to transcription factors and other regulatory proteins, thereby affecting gene activity.

The dynamic nature of nucleosomes allows for modifications, such as acetylation, methylation, and phosphorylation, which can alter chromatin structure and influence gene expression patterns. These modifications are central to processes like gene regulation, DNA repair, and chromosomal stability.

Overall, nucleosomes are essential for DNA packaging in eukaryotic cells and play a vital role in the regulation of genetic activities essential for cell function and development.