Nucleosome

A nucleosome is a chromatin unit in which DNA wraps around a core of histone proteins. It packages DNA and helps regulate access to genetic information.

Histone octamer: A protein complex of two copies each of histones H2A, H2B, H3, and H4. This eight-protein core forms the spool around which nucleosomal DNA wraps.
Chromatin: The complex of DNA, histone proteins, and associated molecules that forms eukaryotic chromosomes. Nucleosomes are the repeating structural units of chromatin.
Gene expression: The processes by which information in a gene produces a functional RNA or protein. Nucleosome placement can make transcription start sites more or less accessible.
Heterochromatin: A compact form of chromatin generally associated with reduced transcriptional activity. Its dense organization contrasts with accessible chromatin containing exposed nucleosomal DNA.
Linker DNA: DNA connecting neighboring nucleosomes along a chromatin fiber. Its length and associated proteins influence spacing between nucleosomes.
DNA: A double-stranded molecule that stores hereditary information in most organisms. The DNA helix bends and wraps around the nucleosome's histone core.
Transcription factor: A protein that binds specific DNA sequences and regulates transcription. Transcription factors often compete with or recruit nucleosomes at regulatory DNA.
Euchromatin: A relatively open form of chromatin that is often transcriptionally active. It contrasts with compact chromatin, though both contain nucleosomes.
Histone H1: A linker histone that binds near DNA entry and exit sites on the nucleosome. H1 helps stabilize wrapped DNA and organize higher-order chromatin.
Histone: A family of basic proteins that bind DNA and help package eukaryotic genomes. Histones provide the positively charged proteins that organize nucleosomal DNA.

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