摘要： 后生效应是近几年才定义清楚的一类现象，指所有那些DNA序列没有改变的基因表达后体细胞的遗传表型发生改变的现象。它对生物体的性状发育如性别决定、着丝粒的功能决定、果蝇复眼发育、朊病毒致病性的获得及癌的发生等等方面有着重要的影响。多方面的研究表明，导致后生效应的可能原因主要有四个方面：DNA的甲基化、组蛋白的乙酰化、染色质结构背景的改变和蛋白质构型的变化。
Abstract：Epigenetic effects,which were defined clearly in recent years,are most often used to denote all those somatically heritable changes in gene expression that do not involve changes in DNA sequence.They affect the development of organismal characters such as sex determination,the functional determination of centromeres,the development of Drasophila's eys,the prion pathogenicity and cancer formation greatly.Studies on many aspects show that there are four main reasons which cause the epigenetic effects;the methylation of DNA,the acetylation of histones,the change of chromatin structure and the alteration of protein configuration.