Lecture05_Nucleic Acids核酸.pdf

第五章核酸的化学 Nucleic Acids 1 Objectives 1. Identify the building blocks of DNA and RNA 2. Know the 3 levels structure of nucleic acids 3. Identify the roles of DNA and RNA 4. Describe Chargaff’s rules 5. Compare and contrast DNA in eukaryotic cell and prokaryotic cell 6. Understand denaturation and renaturation of nucleic acids 7. Briefly outline physical and chemical properties of nucleic acids 2 Watson and Crick James Watson and Francis Crick, crackers of the DNA code, in 1959 DNA 双螺旋结构模型 /medicine/laureates/1962/ 3 Nucleic Acids  2 kinds of nucleic acids: DNA RNA  Nucleic acids are large molecules found in the nuclei of cells  They contain all the information (instructions) for making the complete organism (direct info for cellular growth reproduction)  Each time a cell divides, the information in genome is copied and passed to new cells  All of the genetic information in the cell is called genome(基因组) 4 Nucleic Acids  Genes are the hereditary material within the chromosomes(染色体).  They are essentially long stretches of double-helical DNA  DNA specifies the sequence of RNA, which then determines the protein’s amino acid sequence 5 Hereditary material ？ “四核苷酸假说”：核酸由四种核苷酸组 成的单体构成的，缺乏结构方面的多样性, 不大可能有重要的生理功能。 著名的肺炎球菌实验  1928年，英国  S型肺炎球菌：有荚 膜，菌落表面光滑  R型肺炎球菌：没有 荚膜，菌落表面粗糙  结果说明？ 著名的肺炎球菌实验  结果说明：加热杀死的S型肺炎球菌中一定有某种特殊的 生物分子或遗传物质，可以使无害的R型肺炎球菌转化为 有害的S型肺炎球菌  这种生物分子或遗传物质是什么呢？