what is chromatin fibre in 600 words? ❤
Answers
Chromatin is a mass of genetic material composed of DNA and proteins that condense to form chromosomes during eukaryotic cell division. Chromatin is located in the nucleus of our cells.
The primary function of chromatin is to compress the DNA into a compact unit that will be less voluminous and can fit within the nucleus. Chromatin consists of complexes of small proteins known as histones and DNA.
Histones help organize DNA into structures called nucleosomes by providing a base on which the DNA can be wrapped around. A nucleosome consists of a DNA sequence of about 150 base pairs that is wrapped around a set of eight histones called an octamer.1
The nucleosome is further folded to produce a chromatin fiber. Chromatin fibers are coiled and condensed to form chromosomes. Chromatin makes it possible for many cell processes to occur including DNA replication, transcription, DNA repair, genetic recombination, and cell division.
Euchromatin and Heterochromatin
Chromatin within a cell may be compacted to varying degrees depending on a cell's stage in the cell cycle.
In the nucleus, chromatin exists as euchromatin or heterochromatin. During interphase of the cycle, the cell is not dividing but undergoing a period of growth.
Most of the chromatin is in a less compact form known as euchromatin. More of the DNA is exposed in euchromatin allowing replication and DNA transcription to take place.
During transcription, the DNA double helix unwinds and opens to allow the genes coding for proteins to be copied. DNA replication and transcription are needed for the cell to synthesize DNA, proteins, and organelles in preparation for cell division (mitosis or meiosis).
A small percentage of chromatin exists as heterochromatin during interphase. This chromatin is tightly packed, not allowing gene transcription. Heterochromatin stains more darkly with dyes than does euchromatin.