noun, plural: chromatins
A chromatin is a macromolecule made up of DNA or RNA and proteins. It chromatin can be easily recognized through staining, hence its name, which literally means coloured material. It turns into a chromosome when it becomes condensed during cell division. Its functions are to package DNA into a smaller volume to fit in the cell, strengthen the DNA to allow mitosis and meiosis, and to serve as a mechanism to control expression. The chromatin is found within the cell nucleus of eukaryotic cells.
The basic structural unit of a chromatin is the nucleosome. Each nucleosome in a chromatin is made up of a DNA segment wound around the histone protein cores. There are two forms of chromatins in the interphase nucleus: euchromatin and heterochromatin. The form of chromatin that is structurally loose is referred to as euchromatin. It is usually active in terms of transcription and replication. It is loose to allow RNA and DNA polymerases to, respectively, transcribe and replicate DNA. The heterochromatin is the less active chromatin. It bears inactive genes and is relatively more condensed.
Word origin: Greek khrōma, khrōmat- ("color") + -in