Chromatin is a complex of macromolecules found in cells, consisting of
DNA,
protein, and
RNA. The primary functions of chromatin are 1) to package DNA into a smaller volume to fit in the cell, 2) to reinforce the DNA macromolecule to allow
mitosis, 3) to prevent DNA damage, and 4) to control
gene expression and DNA replication. The primary protein components of chromatin are
histones that compact the DNA. Chromatin is only found in
eukaryotic cells (cells with defined nuclei).
Prokaryotic cells have a different organization of their DNA (the prokaryotic chromosome equivalent is called
genophore and is localized within the
nucleoid region).