分子生物学双语复习知识点.doc

生命基本特征（本质）：生命是生物体所表现出来的复合现象，包括：自身繁殖，生长发育，新陈代谢，遗传变异，对刺激产生反应等生物学Biology：是一门研究生命的现象与本质及活动规律的科学。它包揽了生命的各个方面，从生命的化学组成，细胞的结构与功能，个体生物学，生物的多样性，到生物的遗传、进化及生态等方面的完整知识体系。分子生物学Molecular Biology：它是研究核酸、蛋白质等生物大分子的结构与功能，并从分子水平上阐述蛋白质与核酸、蛋白质与蛋白质之间相互作用的关系及其基因表达调控机制的学科，是人类从分子水平上真正揭开生物世界的奥秘，由被动地适应自然界转向主动地改造和重组自然界的基础学科。Is a subject to understand the five basic cell behavior patterns (growth, division, specialization, movement, and interaction) in terms of the various molecules that are responsible for them. That is, molecular biology wants to generate a complete description of the structure, function, and interrelationships of the cells macromolecules, and thereby to understand why living cells behave the way they do.分子生物学的研究内容Research Contents of Molecular Biology ：生物大分子的结构功能研究（结构部分，又称结构分子生物学）：包括基因、基因组的结构；DNA 复制、 转录 、翻译（功能部分）；基因表达调控研究（调控部分）；DNA重组技术（又称基因工程）Structure and Function of Macromolecules(Structural Part, Also Known as Structural & Molecular Biology)；DNA Replication,Transcription, Translation(Functional Part)；Regulation of Gene Expression(ControlSection)；RecombinantDNATechnology(Genetics)F.Miescher就发现了核素（nuclein）；Boyer 和Berg等发展了重组DNA技术，完成了第一个细菌基因的克隆；Sanger 等发明了DNA测序技术；Sanger、Maxam和Gilbert先后发明了三种DNA序列的快速测定法；Mullis等发明的聚合酶链式反应（PCR）；90年代全自动核酸序列测定仪问世；生物芯片技术是生命科学研究中继基因克隆技术、PCR技术、基因自动测序技术后的又一次革命性技术突破；分子遗传学基本理论建立者Jacob和Monod最早提出的操纵元学说分子生物学的3条基本原理：构成生物体各类有机大分子的单体在不同生物中都是相同的；生物体内一切有机大分子的建成都遵循共同的规则；某一特定生物体所拥有的核酸及蛋白质分子决定了它的属性。Hierarchical nature of cellular structures and their assembly：Small molecules（Strong covalent bonding） Macromolecules（Weaker interactions） Supramolecular Structures Subcellular organelles Cell真核细胞含遗传物质：nucleus核 、Nucleolus核仁、80S ribosome核糖体、endoplasmic reticulum内质网、Golgi apparatus高尔基氏体原核细胞含遗传物质：nucleoid拟核 、70S ribosome核糖体、质粒 plasmid生物大分子Macromolecules：天然合成的、分子量在1041012的有机物，包括核酸、蛋白质和多糖。微管Microtubules：are found in arrays radiating from the nucleus, in the spindle 纺锤 apparatus and in the basal bodies of cilia 纤毛微丝Microfilament(Actin filament 肌纤维) ：are found around the periphery of the cell, they also form the contractile 有收缩性的 element of skeletal muscle. 中间纤维Intermediate filaments：are seen as cables stretching舒展across the cell 非共价作用力Noncovalent interactions：to determine the three-dimensional structures of proteins and nucleic acids；离子键Ionic Bonds氢键Hydrogen-Bonding ，疏水作用力Hydrophobic Interaction Van der Waals Attraction 范德华力Three major classes of macromolecules：构型Configuration：一个分子中原子或基团的特定空间排布。氨基酸的基本构型：L-型 和 D-型，Mainly L-amino acid in nature.甘氨酸中的-C是对称的，无L-型和D-型之分。构象Conformation：组成分子的原子或基团绕单键旋转而形成的不同空间排布。一级结构Primary Structures: Refers to its amino acid sequence.多肽Polypeptide : A polymer consisting of several amino acids.残基Residue: The amino acid in a peptide.一级结构内容The contents of the primary structure：组成蛋白质的多肽链数目；每一条多肽链中末端氨基酸的种类；每一条多肽链中氨基酸的数目、种类和排列顺序；链内和链间二硫键的位置和数目。Molecular weight 15,00070,000 Average M.W. of an amino acid is 110.Three rules of folding：肽键平面；侧链空间；电荷相邻性General tendencies of folding：侧链：极性与非极性；氢键；二硫键helix features: A right handed helix with 3.6 AA residues per turn such that each peptide bond C=O (or N-H) group is hydrogen bonded to N-H (or C=O) of the peptide bond three residues away.The distance between two turns is 0.54 nm.折叠sheet：is formed by hydrogen bonding of the peptide bond N-H and C=O groups to the complementary groups of another section of the peptide chain.折叠结构特征：氢键主要是由两条肽链之间形成的；也可以在同一肽链的不同部分之间形成;几乎所有肽键都参与氢键的交联，氢键与链的长轴接近垂直;肽链的主链呈锯齿状折叠构象; 碳原子总是处于折叠的角上，氨基酸的R基团处于折叠的棱角上并与棱角垂直; 两个氨基酸之间的轴心距为 0.35 nm。维持蛋白质空间结构的化学键Bonds determine the three-dimensional structures of a protein：键能高的化学键可保证蛋白质空间构象的稳定性；键能小的化学键则可使蛋白质构象具有一定的灵活性：Hydrogen Bond ，Van der Waals Attraction，The Hydrophobic Interaction，Ionic Bonds (Electrostatic interactions )，Disulfide bonds 二硫键，Metal-ion coordination complexes 配位键不同氨基酸形成 -螺旋的倾向性不同，一级结构不同，则功能不同H (Heavier) chain: 由440个氨基酸组成 L (Lighter) chain:由214个氨基酸组成抗体功能区Function Fragments of Antibody ：antigen binding sites，Complement 补体 binding site，Binding to Fc receptors免疫球蛋白Immunoglobulin, Ig：具有抗体活性或化学结构与抗体相似的球蛋白Theories of formation of the enzyme-substrate complex：Lock-and-key models；Induced-fit models核苷酸的生物学功能：作为核酸的单体；细胞中的携能物质（如ATP、GTP、CTP、GTP）；酶的辅助因子的结构成分（如NAD）(nicotinamide adenine dinucleotide, 烟酰胺腺嘌呤二核苷酸)；细胞通讯的媒介（如cAMP、cGMP）碱基互补配对：碱基位于双螺旋的内侧，嘌呤和嘧啶碱基彼此密切相近。一股链中的嘌呤与另一股链中嘧啶之间以氢链相连DNA双螺旋主要内容：(1) 两股DNA链围绕一假想的共同轴心形成一右手螺旋结构，双螺旋的螺距为3.4nm，直径为2.0nm。(2) 链的骨架由亲水的脱氧核糖基团和磷酸基团构成，位于双螺旋的外侧。(3) 碱基位于双螺旋的内侧，嘌呤和嘧啶碱基彼此密切相近。一股链中的嘌呤与另一股链中嘧啶之间以氢链相连，称为碱基互补配对；碱基对层间距离为0.34nm。碱基互补配对总是腺嘌呤与胸腺嘧啶之间(A=T)，形成两个氢键；或者鸟嘌呤与胞嘧啶之间(G=C)，形成三个氢键。(4) 方向：DNA双螺旋中的两股链走向是反向平行的，一股链是53走向，另一股链是35走向。(5) 两股链之间在空间上形成一条大沟和一条小沟.The G+C content :The proportion of G is always the same as the proportion of C in DNA, and the proportion of A is always the same as that of T. So the composition of any DNA can be described by the proportion of its basesDouble-strand DNARight-handed helix: B，A，C，D，E formLeft-handed helix: Z form A-DNA、B-DNA和Z-DNA结构特征核酸一般不含元素S；核酸中P元素的含量较多并且恒定，约占910%。核酸定量测定的经典方法，是以测定P含量来代表核酸量。DNA结构的不均一性heterogeneity：1.反向重复序列(inverted repeats)又称回文序列(palindrome)通常是作为一种特别信号，如限制性内切酶及调节蛋白的识别位点，转录终止信号等Cruciform(十字形的)；2.富含A/T的序列，在很多有重要调节功能的DNA区段都富含AT，特别是在复制起点和启动子的序列中，其对于复制和起始十分重要。因为AT对只有二条氢键，易于解开，利于起始复合物的形成；3.嘌呤和嘧啶的排列顺序对双螺旋结构稳定性的影响，从嘌呤到嘧啶的方向的碱基堆集作用显著大于同样组成的嘧啶到嘌呤方向的碱基堆集作用（5GC3稳定性远大于5CG3）Three primary types of RNA：rRNA: 3 or 4；tRNA: up to 50；mRNA: over 1,000tRNA二级结构三叶草结构；三级结构L型结构Ribozyme 核酶：是具有催化功能的RNA分子，是生物催化剂。又称核酸类酶、酶RNA、 核酶类酶RNA。 它的发现打破了酶是蛋白质的传统观念核酸特性： Stability：H-bonds determine the specificity of the base pairing.hydrophobic and dipoledipole （偶极）interactions；Viscosity：DNA solutions have a high viscosity；Buoyant density：1.7 g cm3核酶Ribozyme：是具有催化功能的RNA分子，是生物催化剂。又称核酸类酶、酶RNA、 核酶类酶RNA。 它的发现打破了酶是蛋白质的传统观念。因为嘌呤和嘧啶环中含有共轭双键，260nm测吸光度值，碱基的这一特性常被用来对碱基、核苷、核苷酸和核酸进行定性和定量分析浓度1 mg / ml：double-stranded DNA has A260 = 20；RNA and single-stranded DNA have A260 = 25浓度50g/ml：双螺旋DNA：A260=1.00；完全变性DNA(单链DNA)：A260=1.37；单核苷酸的等比例混合物：A260=1.60A260/A280 ratio of a double-stranded DNA sample测纯度：=1.8 - Pure DNA； above 1.8 suggest RNA contamination，below 1.8suggest protein contamination增色效应Hypochromicity：DNA变性发生在一个狭窄的范围内，在变性过程中，DNA在260nm的吸收值先是缓慢上升，到达某一温度后骤然上升解链温度（Tm值）Melting temperature: 通常将核酸加热变性过程中，紫外光吸收值达到最大值的50%时的温度称为核酸的解链温度，由于这一现象和结晶的融解相类似，又称融（熔）解温度.is the mid-point (A260=1.185 ) of the transition when duplex DNA to denatured by heating to separate into single strands.当GC含量在30%-70%之间，溶液为0.15M的NaCl+0.015M的柠檬酸钠，对于特定核酸分子：Tm = 69.30.41(G+C%)影响Tm因素：GC content；Length of DNA一定条件下(相对较短的核酸分子)，核酸分子越长，Tm值越大；Ionic concentration 离子强度，溶液的离子强度较低时，Tm值较低，融点范围也较宽、DNA制剂不应保存在离子强度过低的溶液中； pH；DenaturantDNA变性Denaturation of DNA or RNA：指DNA分子由稳定的双螺旋结构松解为无规则线性结构的现象。变性时维持双螺旋稳定性的氢键断裂，碱基间的堆积力遭到破坏，但不涉及到其一级结构的改变describes its conversion from the double-stranded to the single-stranded state.复性Renaturation: 指变性DNA在适当条件下，二条互补链全部或部分恢复到天然双螺旋结构的现象，它是变性的一种逆转过程 is the reassociation of denatured complementary single strands of a DNA double helix.DNA-RNA hybridization : To detect an RNA molecule that has been copied from a particular DNA molecule.退火annealing：热变性DNA一般经缓慢冷却后即可复性凡能破坏双螺旋稳定性的因素均可引起核酸分子变性：Thermal denaturation；极端的pH；Chemical denaturation变性特性：超螺旋结构解旋，氢键断裂；溶液粘度降低；溶液旋光性发生改变影响复性因素：Temperature and time：25 lower than Tm ，the cooling is sufficiently slow；Concentration of DNA 浓度；Conformity of DNA base sequence 均一性（复性后大部分不是原配链）principle of the hybridization reaction：to expose two single-stranded nucleic acid preparations to each other ；to measure the amount of double-stranded material that forms.Primary structure：the sequence of nucleotides；the direction of the DNA strands is from 5 - P terminus to 3-OH Secondary structure：double helix: Linear，Circular，triple helixTertiary structure：Supercoil正超螺旋Positive supercoiling: when the DNA is twisted in space in the same sense as the strands are wound around one another, causes the double helix to be more tightly wound. 负超螺旋Negative supercoiling: when the DNA is twisted in space in the opposite sense from the internal winding of the strands, causes the double helix to be les tightly wound. Negative supercoiling can be thought of as creating tension in the DNA that is relieved by unwinding the double helix. DNA超螺旋的意义：超螺旋的引入提高了DNA的能量水平，可实现松弛态DNA所不能实现的结构转化。正超螺旋可使DNA形成高度致密的状态而折叠于有限的空间；负超螺旋产生的结构张力促进了双螺旋链的解旋。拟核，类核nucleoid：细菌染色体在细胞内形成的一个致密区域大肠杆菌染色体大小4.6106 bp染色质Chromatin： is the highly ordered DNAprotein complex which makes up the eukaryotic chromosomes，composed of DNA, proteins, and a small amount of RNA压缩率packing ratio: the length of the DNA divided by the length of the unit that contains it.核小体Nucleosome： is the basic structural subunit of chromatin, consisting of 200 bp of DNA and an octamer of histone proteins.11nm in diameter and 6nm high 150-240 base-pairs Core particle：Core DNA : 146 nucleotide pairs；Octameric disc :Two molecules each of H2A, H2B, H3, and H4；Linker DNA:10100 bp (55bp)；H1组蛋白Histones：are conserved DNA-binding proteins of eukaryotes that form the nucleosome, the basic subunit of chromatin.非组蛋白Nonhistones：include all the proteins of chromatin except the histones.非特异性结合蛋白：组蛋白，拓扑异构酶特异性结合蛋白：Polymerases；Regulatory proteins；Certain nucleases ( Restriction endonucleases)DNA包装为染色体：核小体 螺线体（ Solenoid 螺线管） 超螺线体 染色体Euchromatin 常染色质：碱性物质染色浅，解螺旋而松散的，是比较活跃的区域Heterochromatin 异染色质：碱性物质染色深。高度螺旋化，不是活跃的区域基因gene：是核酸中贮存遗传信息的遗传单位，是贮存有功能的蛋白质多肽链或RNA序列信息及表达这些信息所必需的全部核苷酸序列基因组Genome:细胞或生物中，一套完整单倍体遗传物质的总和（包括一种生物所需的全套基因及间隔序列）；结构：主要指不同的基因功能区域在核酸序列中的分布和排布情况；功能：贮存和表达遗传信息等位基因allele： 二倍体细胞有2套基因，一套来自父本，另一套来自母本，每个细胞的全部基因均由2套基因组成，每一对基因称做等位基因。等信基因：由于突变作用引起DNA结构变异，所以某一基因可具有若干种不同的形式，这种同一基因不同的形式互称等信基因。多顺反子mRNA：功能上相关联的多个结构基因受同一启动序列调控，被一起转录和翻译生成多种蛋白质的 mRNA 内含子intron：在转录后的加工中，从最初的转录产物除去的内部的核苷酸序列。外显子exon：既存在于最初的转录产物中，也存在于成熟的RNA分子中的核苷酸序列，是最后出现在成熟RNA中的基因序列, 又称表达序列，可在蛋白质生物合成过程中被表达为蛋白质。外显子就是指真核细胞的基因在表达过程中能编码蛋白质的核苷酸序列卫星DNA：将真核生物DNA切成104 bp的片段，在CsCl密度梯度离心中会出现不同的离心峰，在主峰附近出现的一些小峰就是卫星DNA，高度重复序列，存在异染色体区域基因家族gene family：一组功能相似、核苷酸序列具有同源性的基因,可能由某一共同祖先基因经重复和突变产生。病毒基因组特点：基因组很小，遗传信息量也少，但不同病毒基因组大小差异很大；只含有一种核酸，单链或双链，闭合环状或线状分子；通常有重叠基因；基因之间的间隔序列(spacer sequence)很短；相关基因集中成簇；噬菌体的基因是连续的，但真核细胞的病毒都含有不连续基因。细菌基因组特点：通常由一条环形或线形双链DNA分子组成，类核；有操纵子（operon）结构，多个相关的结构基因串联在一起，受同一调控区调节，合成多顺反子mRNA;具有多种调控区；非编码DNA所占比例很少，且基因是连续的；编码蛋白质的结构基因为单拷贝，但rRNA基因一般是多拷贝的。 真核生物基因组特点：多条线状染色体，分子量很大；含有大量的重复序列；基因是不连续的（断裂基因，有内含子）；单拷贝，单顺反子；具有复杂的调控结构区。基因家族特点：成员可以串联排列在一起，形成基因簇(gene cluster)或串联重复基因，如rRNA、tRNA和组蛋白的基因有些成员也可位于不同的染色体上，如珠蛋白基因；有些成员不产生有功能的基因产物，这种基因称为假基因 (Pseudogene)人线粒体基因组的特点：16，569bp的双链闭环分子，一条链为重链(H链)，一条链为轻链(L链)，两条链均有编码功能，每个mtDNA分别编码13种蛋白质和24种结构RNA (22rRNA，2tRNA)；母系遗传；结构基因不含内含子，部分区域有基因重叠，因此病理性mtDNA突变更易发生；mtDNA突变频率更高；线粒体DNA突变的表型表达与核DNA不同细菌与真核生物基因组特点比较：细菌基因组：通常由一条环形或线形双链DNA分子组成，类核；只有一个复制起始点；有操纵子（operon）结构，多个相关的结构基因串联在一起，受同一调控区调节，合成多顺反子mRNA；编码蛋白质的结构基因为单拷贝，但rRNA基因一般是多拷贝的；真核生物基因组：多条线状染色体，分子量很大；DNA与蛋白质结合稳定，形成高级结构；有多个复制起点(ori)；具有多种调控区；存在核膜，转录和翻译在时间和空间上被分隔，不偶联；单拷贝，单顺反子；含有大量的重复序列；基因是不连续的（断裂基因，有内含子）可移动的基因；非编码DNA所占比例很少；基因是连续的；无核膜，无转录后加工，转录和翻译偶联；具有可移动的DNA序列组分。Several key experiments led to this realization：1.Griffiths experiments (1928)肺炎双球菌转化实验：S有毒，R无毒；结果：The living bacteria acquired the genes specifying synthesis of the capsule of the dead cells. -Transforming principle2.The transformation experiment (1931)：S提取物+活R；结果：S细胞提取物含有转化因子3.Avery, Macleod, and McCartys experiments (1944)：分离蛋白质和核酸；结果：Two hereditary molecule candidates: protein or nucleic acid4.The Hershey-Chase Blender Experiment (1952)：Bacteriophages are grown in radioactive medium Proteins labeled with 35S ；DNA labeled with 32P结果：The active component of the bacteriophage that transmits the infective characteristic is the DNA. There is a clear correlation between DNA and genetic information.5. Chargaffs Rules (1952)：the biochemist Erwin Chargaff discovered that different species have different concentrations of the four nitrogen bases: adenine (A), thymine (T), guanine (G), and cytosine (C).A = T and G = C 6.Watson, Crick & Franklin DNA double helix model (1953)DNA适合作为遗传物质的特性：Has the ability to store genetic information；This information can be transmitted to daughter cells with minimal error；Possesses both the physical and chemical stability；Has the potential for heritable change without lose of parental information.遗传物质的特性：Storage and Transmission of Genetic Information by DNA；Transmission of Information from Parent to Progeny by DNA；The Physical and Chemical Stability of Nucleic Acids ；The Ability of DNA to Change: Mutation半保留复制semi-conservative replication：分别以两条亲本链为模板，合成二个新链，新形成的双链中，一条是原来的亲本链，一条是合成的新链。半不连续复制Semi-discontinuous replication：DNA 复制在合成先导链（leading strand) 时是连续的；而在合成后随链(lagging strand)时是先形成小片段（ Okazaki fragment ），随后再将它们连接而成大片段。因后随链是不连续合成的而先导链是连续合成的，所以我们称之为半不连续复制。复制子Replicon：DNA中发生一次复制的单位称为复制子is a unit of the genome in which DNA is replicated；contains an origin for initiation of replication and a terminus at which replication stops复制眼Replication eye：在一个长的未复制区域内已经复制的DNA区域。复制叉Replication fork：双螺旋DNA两条亲本链分开使复制能进行的部位。先导链Leading strand of DNA：is synthesized continuously in the 5-3 direction随从（后滞）链Lagging strand of DNA：is synthesized discontinuously in the form of short fragments (5-3) that are later connected covalently冈崎片段Okazaki fragments：are the short stretches of 1000-2000 bases produced during discontinuous replication; they are later joined into a covalently intact 完整的 strand.复制叉移动方向Direction of replication：单起点、单方向；双起点、双方向；多起点、单方向；单起点、双方向；多起点、双方向Speed of replication ：原核50,000bp/min 真核1000-3000bp/min相差20到50倍，区别是复制子数目和起点是否连续发动复制拓扑异构酶Topoisomerases：是一类改变DNA拓扑性质的酶,在体外可催化DNA的各种拓扑异构化反应，而在生物体内它们可能参与了DNA的复制与转录。它既能水解 、又能连接磷酸二酯键分类：Topo I型：切开双螺旋的一条链，改变一个互绕数；Topo II型：切开双螺旋两条链，改变两个互绕数DNA聚合酶DNA polymerase：is an enzyme that can synthesize a new DNA strand on a template strand校阅作用Proofreading ：refers to any mechanism for correcting errors in protein or nucleic acid synthesis that involves scrutiny 详细审查 of individual units after they have been added to the chain. 缺口平移Nick translation：describes the ability of E. coli DNA polymerase I to use a nick as a starting point from which one strand of a duplex DNA can be degraded and replaced by resynthesis of new material.Pol 3大肠杆菌最重要的复制酶，由十种亚基组成，亚基决定了Pol III全酶的持续合成能力原核生物中的三种DNA聚合酶：引物酶primase：is an RNA polymerase which catalyzes the synthesis of a short RNA segment that are used as primers for DNA synthesis.引物Primer: a short RNA oligonucleotide that consists of 1 to 60 bases, is required for chain initiation during DNA replication.Origin of replication (ori): Initiation occurs at specific base sequences, which comprises the so-called ori. oriC: A 9 nucleotide sequence binded by DnaA protein for initiation of DNA replication, which is repeated 4 times within a 250 nucleotide sequence in E.coli genome . 引发体的形成Formation of the primosome：起始需要解链酶 、单链结合蛋白和引物酶DnaA蛋白是复制起始的关键蛋白，特异性识别oriC。Hu proteins help DnaA bending to double strand DNA - 开放起始复合物在DnaC 的帮助下 DnaB （helicase,解旋酶）六聚体结合于解链区的中间复合物上，DnaB能促进 DnaG (Primase)蛋白结合，完成引发体（primosome ）的形成，合成引物。1.With the help of Hu proteins, Dna A bind to oriC and initiates replication.2.With the help of DnaC，DnaB(helicase,六聚体) bind to open region of DNA and melts duplex DNA .3.With the help of Dna B, DnaG (Primase) binding to ssDNA and synthesizing primers.复制机制Mechanisms of DNA Replication：1.Highly coiled DNA is untwisted by topoisomerase.Initiation of DNA ReplicationWith the help of Hu proteins, Dna A bind to oriC and initiates replication.With the help of DnaC, DnaB (helicase ) bind to open region of DNA and melts duplex DNA.SSB proteins bind to both separated strands.With the help of DnaB, Dna G (Primase) bind to ss DNA and catalyzes formation of RNA primer(limited in 814 nt).2.ElongationA. Leading strand:Primer is synthesized by RNA polymerase.Pol III extends the growing strand until the turminus.B. Lagging-strandPrimer is synthesized by primase.Pol III extends the growing strand until the RNA nucleotide of the primer of the previously synthesized precursor fragment is reached.Then, Pol III dissociates from DNA, Pol I continue carries out nick translation to replace RNA primer with DNA, probably proceeding into the deoxy section. DNA Ligase can compete with Pol I and seal the nick.3.TerminationTus binds to ter, where it stops DnaB from unwinding DNA, thus terminates elongation.Replicated circular DNA molecules are separated by type II topoisomerases.原核生物DNA复制：1) Topoisomerases 拓扑异构酶 untwist解开 highly coiled DNA.2) Initiation of synthesis occurs at ori. 3) Helicase 解旋酶 unwinds double-standed DNA.4) ssb 单链DNA蛋白 attach to the unwound strands, preventing them from winding back together.5）RNA primers引物 are synthesized by RNA polymerase (leading strand ) and primase 引物酶 (Okazaki Fragments冈崎片段).6) DNA polymerase synthesize daughter strands (both leading strand and Okazaki Fragments).(DNA polymerase also checks the accuracy of its own work!)7) Okazaki fragments (Lagging-stand precursor前导 fragments) are edited by pol I( carrying out nick translation to replace RNA primer with DNA) and ligated连接 by DNA ligase连接酶to form lagging strand.8) Tus binds to ter终止子 , where it provides a contra-helicase反解旋 activity and stops DnaB from unwinding DNA. 端粒Telomeres ：真核生物染色体末端的蛋白质-DNA结构，其功能是完成染色体末端的复制，可以防止染色体融合、重组或降解。端粒酶Telomerase：是一种自身携带模板的逆转录酶，催化端粒DNA合成，能够在缺少DNA模板的情况下延伸端粒的寡核苷酸片断。is the ribonucleoprotein enzyme that creates repeating units of one strand at the telomere, by adding individual bases to the DNA 3 end, as directed by an RNA sequence in the RNA component of the enzyme. 聚合酶链式反应PCR（Polymerase Chain Reaction） :是指在DNA聚合酶催化下，以母链DNA为模板，以特定引物为延伸起点，通过变性、退火、延伸等步骤，