Such histones are protein components of the spools around which DNA winds in chromosomes, and alterations of histones can render the DNA accessible to the machinery that actiates genes.

• 组蛋白是被DNA缠绕所形成的串珠样结构（核小体nucleosomes）中的蛋白成份（DNA缠绕组蛋白，形成串珠样结构的核小体）。组蛋白的化学修饰使DNA能够接触激活基因的区域。