九十年前,一位瑞典学者在細胞里发現了一种高分子物质,它含有五碳糖,磷酸和四种生物碱的长鏈,称为核酸。后来在所有植物和动物的細胞里,甚至在細菌和病毒这些极小的生物体中也都找到了核酸。核酸有两种,就是去氧核糖核酸和核糖核酸。去氧核糖核酸一般是在細胞核里,在沒有典型的核結构的細菌中是均匀分布着;核糖核酸在核中和細胞质中都有。有的病毒, Ninety years ago, a Swedish scholar discovered a high-molecular substance in cells. It contained a long chain of five carbon sugars, phosphoric acid, and four alkaloids called nucleic acids. Later, nucleic acids were found in cells of all plants and animals, even in tiny organisms such as bacteria and viruses. There are two kinds of nucleic acids, namely DNA and RNA. DNA is generally found in the nucleus and is evenly distributed in bacteria that have no typical nuclear structure; ribonucleic acids are found both in the nucleus and in the cytoplasm. Some viruses,