These are made of chromatin, which combines DNA with a set of proteins known as histones;four similar histones join together to form a cylindrical spool around which the DNA wraps.

• 染色体由染色质组成，而染色质则是DNA被一组称为组蛋白的蛋白质包裹而成：四种相似的组蛋白结合形成一个圆柱形的线缆包裹着DNA。