A chromosome is made up of DNA primarily according to the National Institutes of Health. It is tightly coiled around histones, which are proteins. The histones support the structure of the chromosome.
Chromosomes are primarily composed of DNA, yet they are tightly wrapped up in a coil pattern around proteins that are known as histones. These components provide the structure of a chromosome. It is not possible to see chromosomes with the naked eye. In fact, the majority of what has been learned about chromosomes has come from looking at them under the lens of a microscope as the cell undergoes division. They have two arms that are linked around a central location, which is called a centromere. The "q arm" is the long arm, and the "p arm" is the shorter arm of the chromosome.