Histones

In biology, specifically molecular biology, histones are highly alkaline proteins found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes. 

Schematic representation of the assembly of the core histones into the nucleosome. image: Richard Wheeler/ wikipedia


 They are the chief protein components of chromatin, acting as spools around which DNA winds, and play a role in gene regulation. Without histones, the unwound DNA in chromosomes would be very long (a length to width ratio of more than 10 million to 1 in human DNA). 

A core ore histone H2A/H2B/H3/H4 showing a DNA of 140base pairs wound around it. image: wikipedia

For example, each human cell has about 1.8 meters of DNA, but wound on the histones it has about 90 micrometers (0.09 mm) of chromatin, which, when duplicated and condensed during mitosis, result in about 120 micrometers of chromosomes.

sourcehttp://en.wikipedia.org/w/index.php?title=Histone&oldid=602727810