Nucleosome
Nucleosome
Nucleosome (pronunciation: /ˈnjuːklɪəˌsoʊm/) is a fundamental unit of DNA packaging in Eukaryotes. It is composed of a segment of DNA wound around eight histone proteins and resembles "beads on a string".
Etymology
The term "nucleosome" is derived from the Latin word 'nucleus' meaning 'kernel' or 'core', and the Greek word 'soma' meaning 'body'. It was first coined in the late 1970s to describe the basic unit of DNA packaging in eukaryotic cells.
Structure
A nucleosome is composed of a little less than two turns of DNA wrapped around a set of eight proteins called histones, specifically two each of histones H2A, H2B, H3, and H4. This core particle is connected to the next one via a segment of linker DNA.
Function
The primary function of the nucleosome is to compact DNA within the cell nucleus. By coiling the DNA around histone proteins, the nucleosome allows for efficient packaging of the large amount of DNA within a cell. Additionally, the structure of the nucleosome plays a key role in gene regulation, as it can control access to the underlying DNA sequence.
Related Terms
- Histone: Any of a group of basic proteins found in chromatin.
- Chromatin: The material of which the chromosomes of organisms other than bacteria are composed. It consists of protein, RNA, and DNA.
- Eukaryotes: An organism whose cells contain a nucleus surrounded by a membrane and whose DNA is bound together by proteins into chromosomes.
External links
- Medical encyclopedia article on Nucleosome
- Wikipedia's article - Nucleosome
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