Something about
Each of our cells (or more correctly, nearly all of our cells) contains a copy of this genome, encoded in three billion base pairs of DNA.
This information is precious and must be carefully guarded. Inside our cells, a collection of repair enzymes corrects chemical changes inflicted on the strands by environmental insults.
But the delicate strands must also be protected from physical damage. This is the job of nucleosomes
3D model present :
- molecular surface of nucleosom
- double stranded DNA
Structure
The picture here shows the molecular surface of eight histone proteins, and the DNA that follow the two strands as they circle around the protein octamer. The tails of the eight protein chains, seen extending outward from the center, are actually longer in reality. But, since they are so long and flexible, they are disordered in the crystal and cannot be seen. The one long chain at lower left gives a good indication of what the others might look like, if we were able to see the nucleosome inside a cell. Keep in mind that this structure only includes a short piece of DNA. In reality, these little nucleosomes are arrayed by the millions along long strands of DNA.