# The Nucleosome

Some things in nature are astonishing: a human (A) is 1.75m/5.74ft on average, one of his hairs (B) has a diameter of only 0.1mm/0.004in, that is approx. 20.000 times smaller. Display (C) shows you two cells (green), their DNA in the nucleus is stained blue. Cells vary in shape and sizes, typically they have a diameter of about 20μm. Their nucleus (D) is again smaller, only measuring 5μm from end to end - that is 350.000 times smaller than the 1.75m/5.74ft human. And the DNA in the nucleus needs to be even smaller - right? To some extent yes, because DNA is a very thin fiber but also a particularly long one, that is to say 2m/6.56ft! How to fit 2m/6.56ft of DNA into the nucleus, which is 350.000 times smaller than the average human?

(Source of images: Wikipedia)

The answer is indeed simple: it is all about packaging the DNA in a clever way! Imagine a wool fiber that is very thin as well as very long, but if it is wrapped around a mandrel, it can be efficiently stashed. Of course, there are no mandrels in nature to wind up the DNA, their role is carried out by proteins.

### DNA + proteins = nucleosome

To organize the DNA in the nucleus properly, the DNA is wrapped around specialized proteins. These proteins are called histones, they form a core around which the DNA is wrapped like the wool fiber around the mandrel. In the following example, you can take a look at the complete structure.

Can you identify the double-stranded DNA and the histone core?