Question

which molecules are present in chromatic

Answer 1

Each DNA strand wraps around groups of small protein molecules called histones, forming a series of bead-like structures, called nucleosomes, connected by the DNA strand. Under the microscope, uncondensed chromatin has a "beads on a string" appearance. The string of nucleosomes, already compacted by a factor of six, is then coiled into an even denser structure known as a solenoid that compacts the DNA by a factor of 40. The solenoid structure then coils to form a hollow tube. This complex compression and structuring of DNA serves several functions. The overall negative charge of the DNA is neutralized by the positive charge of the histone molecules, the DNA takes up much less space, and inactive DNA can be folded into inaccessible locations until it is needed.

There are two basic types of chromatin. Euchromatin is the genetically active type of chromatin involved in transcribing RNA to produce proteins used in cell function and growth. The predominant type of chromatin found in cells during interphase, euchromatin is more diffuse than the other kind of chromatin, which is termed heterochromatin. The additional compression of heterochromatin is thought to involve various proteins in addition to the histones, and the DNA it contains is thought to be genetically inactive. Heterochromatin tends to be most concentrated along chromosomes at certain regions of the structures, such as the centromeres and telomeres. Genes typically located in euchromatin can be experimentally silenced (not expressed) by relocating them to a heterochromatin position.

Chromosomes in the microscope