分子生物學(xué)的中心法則ppt課件

1、第三節(jié)分子生物學(xué)的中心法那么 The Central Dogma of Molecular Biology.1) 中心法那么總述2) DNA自我復(fù)制3) 從DNA到RNA(轉(zhuǎn)錄)4) 遺傳密碼5) 從RNA到蛋白質(zhì)(翻譯)6) 基因.一、中心法那么簡介The Central Dogma of Molecular Biology.二、DNA復(fù)制.DNA Replicating Itself Replication，復(fù)制：在親代DNA雙鏈的每一條鏈上按堿基配對而準確地構(gòu)成一條新的互補鏈，結(jié)果生成兩個與親代鏈一樣的DNA雙鏈。.DNA復(fù)制表示圖.DNA的半保管復(fù)制在DNA復(fù)制時，親代DNA的雙螺旋先

2、解旋，然后以每條鏈為模板，按照堿基配對原那么，在這兩條鏈上各構(gòu)成一條互補鏈。在每一個新構(gòu)成的雙螺旋中，一條鏈是從親代DNA來的，另一條是新構(gòu)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的半不延續(xù)復(fù)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.復(fù)制體(replicon)在DNA復(fù)制過程中，由眾多的酶和蛋白質(zhì)參與DNA的復(fù)制造用。復(fù)制體的根本活動包括：1雙鏈的解開；2RNA引物的合成；3DNA鏈的延伸；4切除RNA引物，填補缺口，銜接DNA片段；5切除和修復(fù)錯配堿基。.三、轉(zhuǎn)錄Transcription: making an RNA copy of a DNA sequence Transcription，轉(zhuǎn)錄：以DNA為模板，按堿基配對將其中所含的遺傳信息傳給R

5、NA，構(gòu)成一條與DNA鏈互補的mRNA鏈的過程。.編碼鏈，有義鏈模板鏈，無義鏈.Transcription of a segment of DNA to form a molecule of RNA. 1RNA聚合酶與DNA模板的結(jié)合.2起始.3延伸.4終止.TranscriptionRNA polymerase,RNA聚合酶closed promoter complex,封鎖的啟動子復(fù)合物open promoter complex,開放的啟動子復(fù)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、遺傳密碼The Genetic Code: Translation of RNA code into protein .三聯(lián)體密碼子的特點：1方向性2無標

9、點性3簡并性4通用性5擺動性起始密碼子：ATG。終止無義密碼子：UAAUGAUAG。同義密碼子：編碼同一個氨基酸的幾個密碼子。.五、翻譯Translation is the process of converting the mRNA codon sequences into an amino acid sequence. Translation，翻譯：在RNA控制下，根據(jù)核酸鏈上每三個核苷酸決議一個氨基酸的三聯(lián)體密碼規(guī)那么，合成出具有特定氨基酸順序的蛋白質(zhì)肽鏈的過程。.Protein Synthesis and Protein Processinga). RNA structureb). P

10、rotein synthesisi). Initiation of protein synthesisii). Peptide bond formation; peptidyl transferaseiii). Elongation and termination.RNA類型結(jié)構(gòu)作用mRNA信使RNA單鏈；原核生物的mRNA為多順反子，真核生物的為單順反子。DNA原始遺傳信息的直接接受者；合成蛋白質(zhì)直接模板。tRNA轉(zhuǎn)運RNA二級結(jié)構(gòu)是三葉草型結(jié)構(gòu)；三級結(jié)構(gòu)為倒L型結(jié)構(gòu)。轉(zhuǎn)運氨基酸到核糖體上；通過反密碼子識別mRNA上的密碼子。rRNA核糖體RNA16S (small ribosomal su

11、bunit)23S (large ribosomal subunit)5S (large ribosomal subunit)含量大，維持核糖體的空間結(jié)構(gòu)；使mRNA和tRNA結(jié)合在適當(dāng)位置；識別mRNA上的啟動和終止信號。核糖體是蛋白質(zhì)生物合成的場所；mRNA是合成的模板；tRNA是模板與“合成原料氨基酸之間的接合體。 .mRNA.rRNA原核生物的核糖體為70S，由50S和30S的大小亞基組成；真核生物的核糖體為80S，由60S和40S的大小亞基組成。rRNA是構(gòu)成核糖體的骨架。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合成酶能識別tRNA，并催化反響。對L-氨基酸有極高的專注性，每種氨基酸都有一個專注的酶。氨酰-tRNA合

13、成酶的高度專注性，防止在蛋白質(zhì)合成時錯誤的氨基酸摻入多肽。.Tertiary structureSecondary structuretRNA.Protein synthesis起始延伸終止一個新生肽鏈的誕生，除了必需有mRNA模板，tRNA及核糖體外，還需求許多蛋白因子。如，起始因子(IF)，延伸因子(EF)和終止因子(RF)等的參與。肽鏈合成的方向是N-C,mRNA信號被轉(zhuǎn)譯的方向是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(肽基轉(zhuǎn)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，遺傳功能的單位。它是一種DNA序列，在有些病毒中那么是一種RNA序列，它編碼功能性蛋白質(zhì)或RNA分子。Genome 基因組，染色體組，一個生物體、細胞器或病毒的整套基因；例如，細胞核基因組，葉綠體基因組，噬菌體基因組。.內(nèi)含子外顯子.DNA雙螺旋 DNA是英文 (Deoxyribonucleic Acid) 的縮寫，中文譯為脫氧核糖核酸，是生物的根本遺傳物質(zhì)。DNA分子是雙鏈的螺旋分子。 每一條鏈的根本組成單位為核苷酸，由堿基、脫氧核糖和磷酸基團三部分組成。共有4種不同的堿基：腺嘌呤A、鳥嘌呤G、胸腺嘧啶T和胞嘧啶C。分子生物學(xué)根本知識復(fù)習(xí).分子生物學(xué)根本知識復(fù)習(xí)基因 遺傳功能的單位，它是一段編碼蛋白質(zhì)或RNA分子的DNA序列。蛋白質(zhì) 執(zhí)行生物功能的最重要的生物大分子之一，它是單鏈狀分子，由20種不同的氨基酸組成。.分子生物學(xué)根本知識復(fù)習(xí)中心法那么 遺傳信息由D