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In biology, chromatin is a complex of DNA and protein in eukaryotic cells. The nucleic acids are generally in the form of double-stranded DNA. The major proteins involved in chromatin are histone proteins. In a eukaryotic cell, nearly all DNA is found compacted in chromatin. DNA is packaged into chromatin both to constrain the size of the molecule and to allow the cell to control expression of the chromatin packaged genes


There are three levels of chromatin organization:
  1. nucleosome - beads on a string
  2. 30 nm condensed chromatin fiber
  3. chromosome

Chromatin can be made visible by staining (thus the name).

See also : chromosome -- chromatid -- genetics