第一章分子遗传学基础2010PPT.ppt

Key points Nucleic acids are of two types: DNA and RNA 核酸有两种类型: DNA和RNA DNA usually exists as double helix, with the two strands held together by hydrogen bonds between the complementary bases: A paired with T and G paired with C DNA通常以双螺旋的形式存在, 两股链通过互补碱基间的氢键结合在一起: A与T和G与C配对 The complementarity of the two strands of a double helix makes DNA uniquely suited to store and transmit genetic information from generation to generation双螺旋中两股链的互补使DNA特别适合存储与在世代间传递遗传信息 The two strands of a double helix have opposite chemical polarity双螺旋中两股链有着相反的化学极性 RNA usually exists as a single-stranded molecule RNA通常以单股分子的形式存在 Testing your knowledge The E.coli virus ΦX174 stores its genetic information in single-stranded DNA. When DNA was extracted from ΦX174 virus particles and analyzed, 21 percent of the bases were found to be G residues. From this information, can you determine what percentage of the bases in this DNA were thymine residues? If so, what percentage? If not,why not? Gene structure基因结构 Evolution of the concept of the gene: summary基因概念的发展：概述 Evolution of the concept of the gene: function基因概念的发展：功能 Evolution of the concept of the gene: structure基因概念的发展：结构 A genetic definition of the gene：基因的遗传含义 Complex gene-protein relationships复杂的基因-蛋白质关系 Evolution of the concept of the gene: summary Gene structure基因结构 (a) Typical prokaryotic gene典型的原核生物基因 (b)Typical eukaryotic gene典型的真核生物基因 Gene structure基因结构 The concept of the gene has undergone many refinements since its discovery by Mendel in 1866. Most genes encode one polypeptide and can be operationally defined by the complementation test  从1866年孟德尔定律发现以来基因的概念经历了许多变化，大部分基因编码一条多肽，可以通过互补测验来定义。 Evolution of the concept of the gene: function Mendel: constant factors controlling phenotypic traits孟德尔：控制表型性状的永久因子 Garrod: one mutant gene-one metabolic block加诺德：一个突变基因-一种代谢障碍 Early evidence that enzymes are controlled by genes基因控制酶 Beadle and Tatum: One gene-one enzyme：一个基因-一种酶 One gene-one polypeptide一个基因-一条多肽 Mendel: consta