Chromatin is divided into heterochromatin (condensed) and euchromatin (extended) forms. Hetrochromatin is composed mostly of satellite DNA tandem repeats. The active components of chromatin are DNA and histone proteins, although other proteins also occur. The functions of chromatin are:
- to package DNA into a smaller volume to fit in the cell
- to strengthen the DNA to allow mitosis and meiosis
- to serve as a mechanism to control expression and DNA replication.
Chromatin contains genetic material: instructions to direct cell functions. Changes in chromatin structure are one way the action of genes is controlled.