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一、前言新型病原体类病毒的发病过程和传染方法与一般病毒十分相似,但远较病毒为小,并且它仅由核糖核酸(RNA)构成,1971年首先发现。病毒在核酸之外还包有蛋白质外壳,类病毒则是裸核酸,外面没有蛋白质外壳,其重量也只有最轻病毒重量的1/20;因为它和病毒都带有遗传子核酸,所以命名为类病毒。世界各地已经发现的类病毒共有8种,它们都是核糖核酸性(RNA)的,还没有发现过脱氧核糖核酸(DNA)构成的类病毒。其分子量为10—12万道尔顿,沉降系数为6—10
I. INTRODUCTION The pathogenesis and transmission of new pathogens are very similar to those of the general virus but much smaller than that of the virus. It is only composed of RNA and was first discovered in 1971. The virus contains a protein shell in addition to the nucleic acid, while the viroid is a naked nucleic acid, without a protein shell on it, and weighs only 1/20 of the weight of the lightest virus; because it and the virus contain genetic nuclides, it is named Viroid. There are 8 kinds of viruses that have been found all over the world. All of them are ribonucleic acid (RNA), and no virus like DNA has been found yet. Its molecular weight of 10-12 million Daltons, sedimentation coefficient of 6-10