中文摘要：

通过核移植技术得到的大多数克隆动物在出生前就已经死亡，只有极少数可以发育至妊娠期末或者存活至成年，即使是存活下来的克隆动物也伴有不同程度的发育缺陷和表型异常。DNA甲基化是支配基因正常表达的一种重要的表观遗传修饰方式，是调节基因组功能的重要手段，在胚胎的正常发育过程中具有显著作用。通过对DNA甲基化模式的研究，人们发现克隆动物中存在着异常的DNA甲基化状态，而这些异常的DNA甲基化模式可能就是导致克隆胚早期死亡以及克隆动物发育畸形的主要原因。文章主要论述了DNA甲基化的作用，克隆动物中异常的DNA甲基化模式，以及造成克隆胚胎甲基化异常的原因等问题。

英文摘要：

Most cloned animals by nuclear transfer were dead before their births, and only a few can develop to their late gestation or adulthood. Although some cloned offsprings can survive, they often have some development disfigurements and abnormal phenotypes in various degrees. DNA methylation is an important modifiable manner of epigenetic dominating the correct expression of gene. It is a main instrument of regulating genome function and plays a prominent part in the embryonic normal development. Through researching the pattern of DNA methylation, we found that there were many abnormal DNA methylation patterns in cloned animals, which might be the primary reasons for inducing premature death of cloned embryos and development abnormalities of cloned animals. This article discusses the function of DNA methylation, the aberrant DNA methylation patterns in cloned animals, and the reasons of inducing abnormal DNA methylation in cloned animals.