Euchromatin
Euchromatin
Euchromatin (pronounced: yoo-KROH-muh-tin) is a type of chromatin that is rich in gene concentration and is often (but not always) transcriptionally active. The term "euchromatin" is derived from the Greek words "eu", meaning true or good, and "chroma", meaning color. This is because euchromatin stains less intensely than heterochromatin under a microscope due to its less compact structure.
Structure
Euchromatin is composed of a less condensed form of chromatin fiber, which allows for the active transcription of genes. It is characterized by the presence of a high ratio of genes, and is found in the inner body of the nucleus. The less condensed form is due to the lower level of methylation and higher level of acetylation of the histone proteins around which the DNA is wound.
Function
The primary function of euchromatin is to facilitate transcription, the process by which the information in a DNA sequence is copied into messenger RNA (mRNA). Because the DNA in euchromatin is not as tightly packed as in heterochromatin, it is more accessible to the RNA polymerase enzyme that synthesizes mRNA. This makes euchromatin a key player in the expression of genes.
Related Terms
- Chromatin: The material of which the chromosomes of organisms other than bacteria are composed. It consists of protein, RNA, and DNA.
- Heterochromatin: A tightly packed form of DNA or chromatin, which comes in multiple varieties. These varieties lie on a continuum between the two extremes of constitutive and facultative heterochromatin.
- Gene: A unit of heredity which is transferred from a parent to offspring and is held to determine some characteristic of the offspring.
- Nucleus: A specialized structure occurring in most cells (except bacteria) and separated from the rest of the cell by the nuclear membrane. This membrane seems to be continuous with the endoplasmic reticulum (a netlike structure in the cytoplasm of animal cells) and has pores, which probably permit the entrance of large molecules.
- Histone: Any of a group of basic proteins found in chromatin.
- Messenger RNA (mRNA): A subtype of RNA. An mRNA molecule carries a portion of the DNA code to other parts of the cell for processing.
- RNA polymerase: An enzyme that is responsible for making RNA from a DNA template.
External links
- Medical encyclopedia article on Euchromatin
- Wikipedia's article - Euchromatin
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