Histones are basic proteins, and their positive charges allow them to associate with DNA, which is negatively charged. Some histones function as spools for the thread-like DNA to wrap around.

What causes DNA to wrap around histones?

The tight wrapping of DNA around histones is to a large degree a result of electrostatic attraction between the positively charged histones and negatively charged phosphate backbone of DNA. Histones may be chemically modified through the action of enzymes to regulate gene transcription.

What is wrapped around DNA?

The process starts when DNA is wrapped around special protein molecules called histones. The combined loop of DNA and protein is called a nucleosome. Next the nucleosomes are packaged into a thread, which is sometimes described as "beads on a string". The end result is a fiber known as chromatin.