分子生物学的中心法则ppt课件

1、第三节分子生物学的中心法那么 The Central Dogma of Molecular Biology.1) 中心法那么总述2) DNA自我复制3) 从DNA到RNA(转录)4) 遗传密码5) 从RNA到蛋白质(翻译)6) 基因.一、中心法那么简介The Central Dogma of Molecular Biology.二、DNA复制.DNA Replicating Itself Replication，复制：在亲代DNA双链的每一条链上按碱基配对而准确地构成一条新的互补链，结果生成两个与亲代链一样的DNA双链。.DNA复制表示图.DNA的半保管复制在DNA复制时，亲代DNA的双螺旋先

2、解旋，然后以每条链为模板，按照碱基配对原那么，在这两条链上各构成一条互补链。在每一个新构成的双螺旋中，一条链是从亲代DNA来的，另一条是新构成的。.355 33 5533553leading strand (synthesized continuously)lagging strand (synthesized discontinuously)Each replication fork has a leading and a lagging strand The leading and lagging strand arrows show the direction of DNA chain

3、elongation in a 5 to 3 direction The small DNA pieces on the lagging strand are calledOkazaki fragments (100-1000 bases in length)replication forkreplication forkDNA的半不延续复制.RNA primer533535direction of leading strand synthesisdirection of lagging strand synthesisreplication fork.5353Movement of the

4、replication fork.Movement of the replication forkRNA primerOkazaki fragmentRNA primer5.复制体(replicon)在DNA复制过程中，由众多的酶和蛋白质参与DNA的复制造用。复制体的根本活动包括：1双链的解开；2RNA引物的合成；3DNA链的延伸；4切除RNA引物，填补缺口，衔接DNA片段；5切除和修复错配碱基。.三、转录Transcription: making an RNA copy of a DNA sequence Transcription，转录：以DNA为模板，按碱基配对将其中所含的遗传信息传给R

5、NA，构成一条与DNA链互补的mRNA链的过程。.编码链，有义链模板链，无义链.Transcription of a segment of DNA to form a molecule of RNA. 1RNA聚合酶与DNA模板的结合.2起始.3延伸.4终止.TranscriptionRNA polymerase,RNA聚合酶closed promoter complex,封锁的启动子复合物open promoter complex,开放的启动子复合物initiationelongationterminationRNA productRNA chains are synthesized in

6、a 5 to 3 direction.Prokaryotic RNA polymerase structureRNA polymerase of E. coli is a multisubunit proteinSubunitNumberRole a 2uncertain b 1forms phosphodiester bonds b 1binds DNA template s 1recognizes promoter and facilitates initiationa2bbsa2bb + sholoenzyme core polymerase sigma factor.RNA polym

7、erase holoenzyme (+ s factor) closed promoter complex (moderately stable) the sigma subunit binds to the -10 region once initiation takes place, RNA polymerase does not need very high affinity for the promoter sigma factor dissociates from the core polymerase after a few elongation reactions elongat

8、ion takes place with the core RNA polymerase open promoter complex (highly stable) the holoenzyme has very high affinity for promoter regions because of sigma factors sigma can re-bind other core enzymesThe sigma cycless.四、遗传密码The Genetic Code: Translation of RNA code into protein .三联体密码子的特点：1方向性2无标

9、点性3简并性4通用性5摆动性起始密码子：ATG。终止无义密码子：UAAUGAUAG。同义密码子：编码同一个氨基酸的几个密码子。.五、翻译Translation is the process of converting the mRNA codon sequences into an amino acid sequence. Translation，翻译：在RNA控制下，根据核酸链上每三个核苷酸决议一个氨基酸的三联体密码规那么，合成出具有特定氨基酸顺序的蛋白质肽链的过程。.Protein Synthesis and Protein Processinga). RNA structureb). P

10、rotein synthesisi). Initiation of protein synthesisii). Peptide bond formation; peptidyl transferaseiii). Elongation and termination.RNA类型结构作用mRNA信使RNA单链；原核生物的mRNA为多顺反子，真核生物的为单顺反子。DNA原始遗传信息的直接接受者；合成蛋白质直接模板。tRNA转运RNA二级结构是三叶草型结构；三级结构为倒L型结构。转运氨基酸到核糖体上；通过反密码子识别mRNA上的密码子。rRNA核糖体RNA16S (small ribosomal su

11、bunit)23S (large ribosomal subunit)5S (large ribosomal subunit)含量大，维持核糖体的空间结构；使mRNA和tRNA结合在适当位置；识别mRNA上的启动和终止信号。核糖体是蛋白质生物合成的场所；mRNA是合成的模板；tRNA是模板与“合成原料氨基酸之间的接合体。 .mRNA.rRNA原核生物的核糖体为70S，由50S和30S的大小亚基组成；真核生物的核糖体为80S，由60S和40S的大小亚基组成。rRNA是构成核糖体的骨架。16S (small ribosomal subunit)23S (large ribosomal subuni

12、t)5S (large ribosomal subunit).Ribosome structureAPPPPPPPPP-sitepeptidyl tRNA siteA-siteaminoacyl tRNA sitemRNA5Small subunit(40S)Large subunit(60S)Ribosome with bound tRNAs and mRNA.The model of tRNA.a.a. +tRNA+ATP氨酰-tRNA+AMP+PPi氨酰-tRNA合成酶氨酰-tRNA合成酶能识别tRNA，并催化反响。对L-氨基酸有极高的专注性，每种氨基酸都有一个专注的酶。氨酰-tRNA合

13、成酶的高度专注性，防止在蛋白质合成时错误的氨基酸掺入多肽。.Tertiary structureSecondary structuretRNA.Protein synthesis起始延伸终止一个新生肽链的诞生，除了必需有mRNA模板，tRNA及核糖体外，还需求许多蛋白因子。如，起始因子(IF)，延伸因子(EF)和终止因子(RF)等的参与。肽链合成的方向是N-C,mRNA信号被转译的方向是5-3。.Protein Synthesis .mRNA5 cap40S subunitMeIF2AUGInitiator tRNA bound to thesmall ribosomal subunit wi

14、th theeukaryotic initiation factor-2 (eIF2)Initiation of protein synthesis: mRNA bindingThe small subunit finds the 5 cap andscans down the mRNA to the first AUG codon.mRNA5 40S subunitMeIF2AUG the initiation codon is recognized eIF2 dissociates from the complex the large ribosomal subunit binds60S

15、subunit.mRNA5 MAUG aminoacyl tRNA binds the A-site first peptide bond is formed initiation is completeGCCAmRNA5 MAUGGCCA氨酰-tRNA. NH2 CH3-S-CH2-CH2-CH O=CPeptide bond formation peptide bond formation is catalyzed by peptidyl transferase(肽基转移酶) peptide bond formation results in a shiftof the nascent p

16、eptide from the P-siteto the A-site NH2 CH3-S-CH2-CH2-CH O=C O tRNA NH2CH3-CH O=C O tRNANCP-siteA-site OH tRNA NHCH3-CH O=C O tRNAP-siteA-site.PUCAPPPPPUCAGCA GGG UAGAPPPPElongationGCA GGG UAG following peptide bond formationthe uncharged tRNA dissociatesfrom the P-site the ribosome shifts one codon

17、 alongthe mRNA, moving peptidyl tRNAfrom the A-site to the P-site; thistranslocation requires theelongation factor EF2 the next aminoacyl tRNA thenbinds within the A-site; this tRNAbinding requires the elongationfactor EF1EF1EF2 energy for elongation is provided bythe hydrolysis of two GTPs: one for

18、 translocation one for aminoacyl tRNA binding.PUCAGCA GGG UAGPPPPTermination when translation reaches the stopcodon, a release factor (RF) bindswithin the A-site, recognizing thestop codon release factor catalyzes the hydrolysisof the completed polypeptide fromthe peptidyl tRNA, and the entirecomple

19、x dissociatesRFPUCAGCA GGG UAGPPPPPPP.六基 因.GeneGene 基因，遗传功能的单位。它是一种DNA序列，在有些病毒中那么是一种RNA序列，它编码功能性蛋白质或RNA分子。Genome 基因组，染色体组，一个生物体、细胞器或病毒的整套基因；例如，细胞核基因组，叶绿体基因组，噬菌体基因组。.内含子外显子.DNA双螺旋 DNA是英文 (Deoxyribonucleic Acid) 的缩写，中文译为脱氧核糖核酸，是生物的根本遗传物质。DNA分子是双链的螺旋分子。 每一条链的根本组成单位为核苷酸，由碱基、脱氧核糖和磷酸基团三部分组成。共有4种不同的碱基：腺嘌呤A、鸟嘌呤G、胸腺嘧啶T和胞嘧啶C。分子生物学根本知识复习.分子生物学根本知识复习基因 遗传功能的单位，它是一段编码蛋白质或RNA分子的DNA序列。蛋白质 执行生物功能的最重要的生物大分子之一，它是单链状分子，由20种不同的氨基酸组成。.分子生物学根本知识复习中心法那么 遗传信息由D