To adapt to various states of chromatin, corresponding histone variants are incorporated in nucleosome, and certain modifications also occur on the variants tails. 對於不同狀態的染色質，核小體中會組裝人相應的組蛋白變體，並且各種組蛋白變體的尾部也能發生多種修飾。
But enough evidence has accumulated to prove that some proteins can in fact copy themselves and that variants of PrP are essential players in spongiform encephalopathies. 但是充足的證據證明，某些蛋白質的確可以自我複製，且普恩蛋白變體在海綿狀腦病上扮演了重要角色。
