Chromatin structure

Chromatin Structure

Chromatin is a complex of DNA and protein that condenses to form chromosomes within the nucleus of eukaryotic cells. It is essential in the processes of cell division, gene expression, DNA replication, and DNA repair.

Composition

Chromatin is composed of repeating units called nucleosomes. Each nucleosome is made up of a segment of DNA wound around eight histone proteins and resembles beads on a string. This structure allows the DNA to be tightly packed into the limited space of the nucleus.

Types of Chromatin

There are two types of chromatin: euchromatin and heterochromatin. Euchromatin is less compact and is associated with active transcription of genes. Heterochromatin is more densely packed and is generally associated with genes that are not being expressed.

Chromatin Remodeling

Chromatin remodeling is a process that involves the rearrangement of chromatin from a condensed state to a transcriptionally accessible state, allowing the transcription machinery to access DNA and effectively form RNA.

Chromatin and Disease

Alterations in chromatin structure can lead to genetic disorders and cancer. For example, changes in the structure and function of heterochromatin have been associated with aging and cancer.

See Also

• Epigenetics
• Histone modification
• Nucleosome
• DNA methylation