分子生物學(xué)期末考試復(fù)習(xí)內(nèi)容-2011

1、Section AProkaryotes：原核生物，沒有成形的細(xì)胞核或線粒體的一類單細(xì)胞生物，the simplest living cellsEukaryotes：真核生物，所有單細(xì)胞或多細(xì)胞的、其細(xì)胞具有細(xì)胞核的生物的總稱；denfined by their possension of membrane-enclosed organelles with specialized metabolic functions.Differentiation:分化，生物體發(fā)育過程中細(xì)胞和組織的結(jié)構(gòu)和功能的變化；in most multicellular eukaryotes, groups of ce

2、lls differentiate during development of the organism to provide specialized functionsGlycerides (甘油酯): 通常指由甘油和脂肪酸（包括飽和脂肪酸和不飽和脂肪酸）經(jīng)酯化所生成的酯類, 是中性脂肪，是血脂肪的成分之一，扮演著貯存與輸送的角色Triglycerides(甘油三酯):是長鏈脂肪酸和甘油形成的脂肪分子。是人體內(nèi)含量最多的脂類，大部分組織均可以利用甘油三酯分解產(chǎn)物供給能量，同時肝臟、脂肪等組織還可以進行甘油三酯的合成，在脂肪組織中貯存Polysaccharides:多糖，單糖以糖苷鍵工價連接的

3、聚合體，其功能主要是作為營養(yǎng)糖源或結(jié)構(gòu)組分。Polymers of simple sugars covalently linked by glycosidic bonds,as untritional sugar stores and as structural materialsGlycoproteins:糖蛋白，既含有蛋白質(zhì)又含有糖，糖基化是蛋白質(zhì)翻譯后修飾的通常形式。Contain both protein and carbohydrate components;glycosylation is the commonest form of post-translational modif

4、ication of proteinsChromatin:染色質(zhì)是構(gòu)成真核生物染色體的原件，是一個由大約等量的DNA與小分子的堿性蛋白質(zhì)所組成的脫氧核蛋白復(fù)合體，the material from which eukaryotic chromosomes are made,is a deoxyribinucleoprotein complex made up of roughyl equal amounts of DNA and small,basic proteins called histonesBiomembranes:生物膜，將磷脂與鞘脂置于水中，會自發(fā)地形成一個極性基團在外、非極性烴

5、鏈在內(nèi)的脂雙分子層，when placed in an aqueous environment,phospholipids and sphingolpids naturally form a lipid bilayer with the polar groups on the outside and the nonpolar hydrocarbon chains on the inside.Hydrogen bonds:氫鍵，在供體基因的一個共價結(jié)合的氫原子和受體基因上一對非成鍵電子之間形成，form between a covalently bonded hydrogen atom on a

6、 donnor group and a pair of nonbonding electrons on an acceptor groupvan der Waals forces:范德華力，電中性分子間的非共價結(jié)合的統(tǒng)稱，noncovalent associations between electrically neutral monleculesHydrophobic interaction:疏水相互作用，指水介質(zhì)中球狀蛋白質(zhì)的折疊總是傾向于把疏水殘基埋藏在分子內(nèi)部的現(xiàn)象，是蛋白質(zhì)-蛋白質(zhì)和蛋白質(zhì)-脂類的相互作用以及核酸結(jié)構(gòu)中的主要穩(wěn)定力，a major sabilizing force i

7、n protein-protein and protein-lipid interactions and in nucleic acidsphospholipid molecule:磷脂分子，由兩分子脂肪酸和一分子磷酸以酯鍵與甘油相結(jié)合，是膜的主要成分，consist of glycerol esterifide to two fatty acids and phosphoric acid and contained in memvraneshydrophilic polar head group and a hydrophobic tail. 親水性極性頭部和疏水尾部，磷脂分子有親水性的極性

8、頭組和疏水尾巴，親水性頭部朝向水相，疏水性尾部避水彼此聚集，形成雙分子層，A phospholipid molecule consists of a hydrophilic polar head group and a hydrophobic tail，When placed in water, the hydrophilic heads tend to face water and the hydrophobic tails are forced to stick together, forming a lipid bilayer.Lipoproteins:脂蛋白，與蛋白質(zhì)結(jié)合在一起形成的脂

9、質(zhì)-蛋白質(zhì)復(fù)合物，is a biochemical assembly that contains both proteins and lipids water-bound to the proteinsDensity gradients:密度梯度，包括速度區(qū)帶離心和等密度離心。速度區(qū)帶離心，混合物被加入離心管中預(yù)先鋪好的適當(dāng)介質(zhì)的濃度（形成密度）梯度頂層。通過離心，不同成分將根據(jù)它們的沉降系數(shù)以不同的速度下沉并形成相互分離的帶或區(qū)帶。建立介質(zhì)密度梯度的目的是為了阻礙分離后組分的擴散混合，并且確保組分的線性分離速率。等密度離心，密度梯度延伸至比混合物中的一個或多個組分大一些的密度，因此這些組分在

10、等于它們自己密度的點達到平衡并且停止移動，在這種情況下，密度梯度可以預(yù)先建立，然后將樣品加在上層，也可以是樣品與梯度物質(zhì)混合在一起離心時自動形成。Functions of Membrane:膜的功能，膜上有膜蛋白，決定了膜的功能：作為激素和神經(jīng)遞質(zhì)等信號分子的受體；作為在吸收物質(zhì)前降解細(xì)胞外分子所需的酶；作為選擇性轉(zhuǎn)運小分子、極性離子和分子的孔或通道；作為細(xì)胞與細(xì)胞相互作用的介質(zhì)（主要是糖蛋白）。Receptors for signaling molecules such as hormons and neurotransmitters; enzymes for degrading extra

11、cellular molecules before uptake of the products; pores or channels for the selective transport of small, polar ions and molecules; mediators of cell-cell interactions (mainly glycoproteins).Section BAmino acids:氨基酸，有一個與質(zhì)子、氨基、羧基相連的手性-碳原子和具有不同的理化特性的側(cè)鏈，在溶液中表現(xiàn)為兩性離子，have a chiral -carbon atom linked to

12、a proton, amino and carboxyl groups, and a specific side chain which confers diifferent physical and chemical properties, behave as zwitterions in solution.Acidicbasicpolarnonpolararomatic amino acids:(酸性aa：Asp, Glu; 堿性aa：Lys, Arg)(中性：His)帶點; 極性aa：Ser, Thr, Asn, Gln, Cys; 非極性aa: Gly, Ala, Val, Leu,

13、Ile, Met, Pro; 芳香族aa: Phe, Tyr, TrpPrimary structure of protein:蛋白質(zhì)的一級結(jié)構(gòu)，多肽中從N端到C端的氨基酸序列，the sequence of amino acids from the N to the C terminus-helix: 螺旋，蛋白質(zhì)中常見的二級結(jié)構(gòu)，常在球蛋白和一些纖維蛋白中發(fā)現(xiàn)，右手螺旋每圈友3.6個氨基酸，在肽鏈的N-H與相隔三個殘基的C=O基團間形成氫鍵以穩(wěn)定其整體結(jié)構(gòu)，the best known secondary structure in proteins, often found in glob

14、ular proteins and in some fibrous proteins, the right-handed -helix has 3.6 amino acids per turn and is stbbilized by hydrogen bonds between peptid N-H and C=O groups three residues apart-sheet: 折疊，蛋白質(zhì)的二級結(jié)構(gòu)，堅硬牢固，是重要的結(jié)構(gòu)蛋白，由肽鏈N-H和C=O基團與肽鏈上另一段互補的基團間以氫鍵維系，the secondary structure in proteins, strong and

15、rigid, important in structural proteins, formed by hydrogen bonding of the peptide bond N-H and C=O groups to the complementary groups of another section of the polypeptide chainParallel -sheet: 正向平行的折疊，多肽鏈中的幾個片段走向相同，the sections of polypeptide chain run in the same directionAntiparallel -sheet: 反向平

16、行的折疊，多肽鏈中的片段走向為N端C端和C端N端，the section of polypeptide chain alternate NC and CNprimary structure: 一級結(jié)構(gòu)，多肽中從N端到C端的氨基酸序列，the sequence of amino acids from the N to the C terminussecondary structure: 二級結(jié)構(gòu)，多肽鏈借助氫鍵排列自己特有的螺旋和折疊片斷，polypeptide chains are able to fold into a number of regular structures which a

17、re held together by hydrogen bondsTertiary structure: 三級結(jié)構(gòu)，不同的二級結(jié)構(gòu)區(qū)域和連接區(qū)的組合折疊成一個確定的三級結(jié)構(gòu)， the different sections of secondary structures and connecting regions fold into a well-defined tertiary structureQuaternary structure: 四級結(jié)構(gòu)，指數(shù)條具有獨立的三級結(jié)構(gòu)的多肽鏈通過非共價鍵相互連接而成的聚合體結(jié)構(gòu)，A structural level wherein several p

18、roteins or polypeptide subunits interact through non-covalent bonds to form one functional protein complexDomains：結(jié)構(gòu)域，是在同一多肽中有限的高度有序結(jié)構(gòu)片段相連而成，在真核生物中常由基因中的不連續(xù)部分(稱為外顯子)來編碼，connected by sections with limited higher order structure within the same polypeptide, often encoded by discrete parts of genes cal

19、led exons in eukaryotesMotif：基序，二級結(jié)構(gòu)元件組合或在蛋白質(zhì)家族的相關(guān)成員中常發(fā)現(xiàn)的氨基酸序列，是在不相關(guān)蛋白湊在一起時實現(xiàn)結(jié)構(gòu)-功能統(tǒng)一的最佳解決方案，are groupings of secondary structural elements or amino acid sequences often found in related members of protein families, represent the best solution to a structural-functional requirement that has been arri

20、ved at independently in unrelated proteinsProtein families：蛋白質(zhì)家族，通過基因復(fù)制和隨后的新基因趨異進化產(chǎn)生，不同物質(zhì)的具有相同功能、承擔(dān)相同生化角色的蛋白質(zhì)家族成員為直向同源（定向進化同源），進化不同但功能類似的蛋白質(zhì)為共生同源（平行進化同源），不同生物體的一個蛋白質(zhì)家族直向同源成員間氨基酸序列的相似程度取決于兩個生物體從共同祖先歧化的時間以及該序列的保守性對蛋白質(zhì)功能的重要性，arise through gene duplication and subsequent divergent evolution of the new g

21、enes, family members in different species theat have retained the same function and carry out the same biochemical role are orthologs while those that have evolved different, but often related functions are paralogs, the degree of similarity between the amino acid sequences of orthologous members of

22、 a protein family in different organisms depengds on how long ago the two organisms diverged from their common ancestor and on how important conservation of the sequence is for the function of the proteinProtein functions: 蛋白質(zhì)功能，酶，可以將生化反應(yīng)速度提高幾個數(shù)量級，enzymes, can enhance the rate of biochemical reactio

23、ns by several orders of magnitude; 信號傳遞，細(xì)胞膜上的受體蛋白質(zhì)可以與來自細(xì)胞外介質(zhì)的配體結(jié)合，通過最終的構(gòu)象改變，在細(xì)胞內(nèi)啟動對應(yīng)于配體的反應(yīng)，signaling, receptor proteins in cell membranes can bind ligands from the extracellular medium and, by virtue of the resulting conformational change, initiate reactions within the cell in response to that ligan

24、d; 轉(zhuǎn)運與儲存，許多分子和離子都以蛋白質(zhì)結(jié)合形式轉(zhuǎn)運和儲存，這樣在需要用它們之前，可以增加溶解性、減小反應(yīng)活性，transport and storage, molecules and ions are transported and stored in a protein-biund form, can enhance solubility and reduce reactivity until they are requiredThe principal properties of proteins used for purification:用于純化蛋白質(zhì)的主要特性，有大小、電荷、疏水

25、性和對其他分子的親和性，大?。z過濾層析），電荷（離子交換層析、等電聚焦、電泳），疏水性（疏水作用），親和性（親和層析），重組技術(shù)（過量表達重組蛋白質(zhì)），size, charge, hydrophobicity, and affinity for other molecules, size(Gel filtration chromatography), charge( ion-exchange chromatoraphy, isoelectric focusing, electophoresis ), hydrophobicity (hydrophobic interaction chrom

26、atography), affinity(affinity chromatography),recombinant techniques(overexpression of the protein greatly)globular proteins:球蛋白，緊湊的、近似球形的、含折疊緊密的多肽鏈，多溶于水，典型的球蛋白含有能特異識別和結(jié)合其他化合物的凹陷或裂隙部位，能在其中找到螺旋fibrous proteins：纖維蛋白，含有呈現(xiàn)相同二級結(jié)構(gòu)的多肽鏈，不溶于水，許多纖維蛋白緊密結(jié)合，為單個細(xì)胞或整個生物體提供機械強度，起著保護結(jié)構(gòu)的作用。Section C:Nucleosides：核苷，由堿

27、基共價結(jié)合于戊糖分子的1位構(gòu)成，RNA中的戊糖為核糖，構(gòu)成核糖核苷，DNA中的戊糖為2-脫氧核糖，形成2-脫氧核糖核苷。堿基+糖分子=核苷。A base covalently bonded to the 1-position of a pentose sugar molecule, in RNA the sugar is ribose and the compounds are ribonucleosdes, in DNA the sugar is 2-deoxyribose and the compounds are 2-deoxyribonucleosids. Base + sugar =

28、 nucleosideNucleotide: 核苷酸，由一個或多個磷酸基團共價結(jié)合到核苷的3位、5為或2位（RNA）形成，堿基+糖分子+磷酸分子=核苷酸。RNA（NTP）, DNA（dNTP）。Nucleosides with one or more phosphate groups covalently bound to the 3-, 5- or, 2- in ribonucleotides, base + sugar + phosphate = nucleotide.Hypochromicity (減色性):減色效應(yīng)，雙鏈DNA相對于單鏈DNA吸收值減少的現(xiàn)象，double-strand

29、ed DNA is hypochromic with respect to single-stranded DNA. （越多鏈，吸收值越小）Hyperchromicity (增色性)：增色效應(yīng)，與減色效應(yīng)相反，ssDNA相當(dāng)于dsDNA是增色的，ssDNA is hyperchromic with respect to dsDNA.Melting temperature (Tm): 溶解溫度/解鏈溫度，DNA分子內(nèi)50%的雙鏈結(jié)構(gòu)被打開, 另外50%的還保持著雙螺旋結(jié)構(gòu)時的溫度, the temperature at which 50% of the DNA molecules from a

30、stable double helix and the other 50% have been separated to single strand molecules.Linker number (Lk, 連接數(shù)): 自然條件下，DNA通常以閉環(huán)形式存在，即兩條單鏈均為環(huán)狀且相互連在一起，相互連接的數(shù)目稱為連接數(shù)，DNA frequently occurs in nature as closed-circular molecules, where the two single strands are each circular and linked together, the number

31、of links is known as Lk.l Intramolecular hydrogen bonding and base stacking are the forces for DNA secondary and tertiary structure.分子內(nèi)氫鍵和堿基堆積是DNA二、三級結(jié)構(gòu)的力量l Hydrogen bonding does not normally contribute the DNA stability, DNA Stability lies in the stacking interactions between base pairs. 氫鍵一般對DNA的穩(wěn)

32、定沒有作用，DNA的穩(wěn)定決定于堿基對之間的堆積作用l Hydrogen bonding contributes to specific structures of DNA and protein, such as -helix, -sheet, DNA double helix, RNA secondary structure.氫鍵對DNA和蛋白質(zhì)的特殊結(jié)構(gòu)有作用，例如螺旋，折疊，DNA雙螺旋，RNA的二級結(jié)構(gòu)l Stacking interaction/hydrophobic interaction between aromatic base pairs/bases contribute t

33、o the stability of nucleic acids.芳香族的堿基對/堿基間的堆積作用/疏水作用有助于核酸的穩(wěn)定l Properties of nucleic acids: strong acid and high temperature (such as perchloric acid HClO4 +100), nucleic Acids will be completely hydrolyzed to bases, riboses / deoxyribose, and phosphate.核酸的性質(zhì)：在強酸性和高溫下（如在高氯酸HClO4 +100），核酸會完全水解為堿基，核糖

34、/脫氧核糖和磷酸l When nucleic acids is at the condition of moderate acid (such as pH 3-4), glycosylic bonds attaching purine (A and G) bases to the ribose ring are broken into apurinic nucleic acids. 當(dāng)核酸在中度的酸性條件下（如pH3-4），連接嘌呤和核糖的糖苷鍵會斷開變成脫嘌呤核酸l High pH denatures DNA and RNA by altering the tautomeric (互變異構(gòu))

35、 state of the bases and disrupting specific hydrogen bonding 強堿條件下DNA和RNA因其堿基的互變異構(gòu)態(tài)的改變以及特異氫鍵被破壞而變性l RNA can be hydrolyzed at higher pH by participation of 2-OH groups in intramolecular cleavage of the phosphodiester backbone.RNA在強堿下水解，2-OH參與磷酸二酯鍵骨架的分子內(nèi)裂解l The conformation (geometry) of the DNA can b

36、e altered while the linking number remains constant. 當(dāng)連接數(shù)不變是，DNA分子的（幾何）構(gòu)象可以發(fā)生改變l The topological change (DLk) in supercoiling of a DNA molecule is partitioned into a conformational change of twist (DTw )and/or a change of writhe (DWr).超螺旋的DNA分子的拓?fù)渥兓?DLk)可以分為構(gòu)象變?yōu)槔p繞(DTw )和/或扭曲(DWr)l According to the r

37、atio of OD260/280, how to evaluate the purity of DNA or RNA samples? 根據(jù)OD260/280的比值，如何去估計DNA或RNA樣品的純度？OD260/280中，純dsDNA為1.8，純RNA為2.0，純蛋白質(zhì)為0.5左右。大于1.8，dsDNA受RNA污染，小于1.8，受蛋白質(zhì)污染。The ratio in pure dsDNA is 1.8, 2.0 in pure RNA, about 0.5 in protein. In dsDNA samples, RNA contaminated when its greater th

38、an 1.8, protein contaminated when its less than 1.8protein-0.5 dsDNA-1.8 pure RNA-2.0 dsDNA和RNA的熱變性（thermal denaturation）；快速和慢速降溫下的DNA復(fù)性（renaturation）隨著溫度升高，RNA的雙鏈部分的堿基堆積會減少，光吸收值增大，短堿基對區(qū)域變性比長區(qū)域快；dsDNA分子末端以及內(nèi)部富含A-T區(qū)域的變性使附近螺旋不穩(wěn)定，在Tm共同變性。冷卻可以使熱變性DNA復(fù)性（復(fù)原），快速降溫，各單鏈配對堿基或小部分與原鏈互補配對，光吸收下降?。宦倮鋮s，兩單鏈互補配對，可以形

39、成完全的雙鏈，具有與原來相同的光吸收值Section DReplicon：復(fù)制子，DNA分子中能獨立進行復(fù)制的最小功能單位，包含一個復(fù)制起始點，有時候還有一個終點，any piece of DNA which replicates as a single unit, contains an origin and sometimes a terminusOrigin:復(fù)制起始點，在單個復(fù)制子內(nèi)的DNA復(fù)制的固定起始位置，所有的起始點都在雙鏈最初解鏈處且均富含AT序列，富含AT的起始點俾富含GC的起始點更易解鏈，the initiation of DNA replication within a

40、replicon always occurs at a fixed point. All orgins contain AT-rich sequences where the strands initially separate, AT-rich are more easily opened than GC-rich regions.Terminus: 終點，兩個復(fù)制叉從起始點向兩個方向進行復(fù)制，隨著雙鏈的解鏈模板被復(fù)制直至終點，two replication forks proceed bidirectionally away from the origin and the strands

41、are copied as they separate until the terminus is reached.RNA priming: RNA引導(dǎo)，前導(dǎo)鏈及所有的后隨鏈片段的DNA合成是都由短的RNA片段引導(dǎo)起始，然后沿DNA模板延伸，有助于保持高度的復(fù)制保真性, the leading strand and all lagging strand fragments are primed by synthesis of a short piece of RNA which is then elongated with DNA, helps to maintain high replica

42、tional fidelity.Replisome (復(fù)制小體): 執(zhí)行DNA復(fù)制功能的、由多種蛋白質(zhì)構(gòu)成的復(fù)合體DnaB: DNA解旋酶，利用ATP水解的能量結(jié)合并解開雙鏈DNA的一種酶，the DNA helicase, the enzymes which use the energy of ATP hudrolysis to move ino and melt dsDNA.Proofreading: 校正，指蛋白質(zhì)或核酸合成中的糾錯機制，有助于維持復(fù)制的高度忠實性，helps to maintain high replicational fidelity.Semi-conservativ

43、e replication:半保留復(fù)制，在DNA復(fù)制中兩條親代鏈分開，分別作為模板指導(dǎo)酶催化的新生互補子鏈的合成，并遵循標(biāo)準(zhǔn)的堿基配對原則，親代鏈分開及新生DNA開始復(fù)制處為復(fù)制叉，模板以35方向被讀，新生鏈以53方向合成，大腸桿菌N標(biāo)記培養(yǎng)，the two parental strands separate and each acts as a template to direct the enzyme-catalyzed synthesis of a new complementary daughter strand following the normal base-pairing ru

44、les, the point at which separation of the strands and synthesis of new DNA takes place is the replication fork, the template strands are read in the 35 direction while the new strands are synthesized 53.Semi-discontinuous replication: 半不連續(xù)復(fù)制，前導(dǎo)鏈從起始點按53方向進行連續(xù)復(fù)制，而后隨鏈不立即復(fù)制，而是被短片段取代，后隨鏈的復(fù)制從復(fù)制叉處開始按53的反方向

45、朝向起點形成第一個岡崎片段，隨著復(fù)制叉的前進，前導(dǎo)鏈繼續(xù)被復(fù)制成連續(xù)長鏈，而后隨鏈片段按反方向以不連續(xù)方式被復(fù)制Okazaki fragments：岡崎片段，在DNA不連續(xù)復(fù)制過程中，沿著后隨鏈的模板鏈合成的新DNA片段，真核生物的岡崎片段長度約為100200 nt，而原核生物的為10002000 ntl Prokaryotic genome is a single circular DNA and contains a single replicon. 原核基因組是一個包含單個復(fù)制子的單環(huán)DNAl Eukaryotic genome contains multiple linear chro

46、mosomes and has multiple replicons on each chromosome. 真核生物基因組包含很多線性染色體，而每個染色體中有很多復(fù)制子l All prokaryotic chromosomes and many bacteriophage and viral DNA molecules are circlular and comprise single replicons. 所有的原核生物染色體、許多噬菌體以及病毒的DNA分子都呈環(huán)形并由單一復(fù)制子構(gòu)成l DNA primase lead to synthesize a short RNA primer fo

47、r synthesis of the leading strand. DNA引發(fā)酶引導(dǎo)一小段的RNA引物合成，引發(fā)先導(dǎo)鏈的復(fù)制l In cell cycle, which phase is for DNA replication? And describe the replication order for euchromatin, heterochromatin Centromeric DNA and telomeric DNA. 在細(xì)胞周期中，DNA的復(fù)制有哪些時期？描述常染色質(zhì)、異染色質(zhì)、著絲點的DNA和端粒DNA的復(fù)制順序有4個時期：G1期、S期、G2期和M期；S期是DNA復(fù)制的時期，

48、在S期的早期主要是常染色質(zhì)的復(fù)制，在S期的較晚期主要是異染色質(zhì)，最后的是著絲粒DNA和端粒DNAS: DNA replicationEarly S-phase: euchromatin replicationLate S-phase: heterochromatin replicationCentromeric and telomeric DNA replicate at last l What are the similarities and differences of DNA replication in prokaryotic and eukaryotic cells? DNA復(fù)制在原

49、核生物和真核生物間的異同？Similarities:1. Semi-conservative replication 半保留復(fù)制2. Semi-discontinuous repliction 半不連續(xù)復(fù)制3. DNA helicase, Ssb DNA解旋酶是Ssb4. RNA priming RNA引物5. Proofreading 矯正Differences:1. Origin (single/multiple) 復(fù)制起點：單個/多個2. Initiation (multiple/one times) licensing factor 起始（多次/一次）許可因子3. Rate of re

50、plication fork movement (900/50 nt/S) 復(fù)制叉的移動速度（900/50 nt/s）(50,000/3,000 bp/min)4. Size of Okazaki fragments (1000-2000/100-200 nt) 岡崎片段的大小（1000-2000/100-200 nt）5. Telomeres and telomerases 端粒和端粒酶6. Polymerases (simple/complex) 聚合酶（簡單/復(fù)雜）Section EMutagenesis: 誘變，用物理、化學(xué)和生物因子使基因發(fā)生突變的過程，an event capabl

51、e of causing a mutationDirect mutagenesis:直接誘變，如果一種堿基類似物或配對特性與親本鏈堿基不同的修飾堿基在復(fù)制叉通過之前未被DNA修復(fù)機制去除，結(jié)果會引入一個錯配堿基，而第二輪復(fù)制會將這突變永遠(yuǎn)固定下來，if a base analog or modified base whose base pairing properties are different from the parent base is not removed by a DNA repair mechanism before passage of a replication fork

52、, then an incorrect base will be incorporated, a second round of replication fixes the mutation permanently in the DNAIndirect mutagenesis:間接誘變，在復(fù)制叉通過之前，DNA中的大部分損傷都會被直接地?zé)o錯恢復(fù)或切除修復(fù)機制所修復(fù)。如果未能被修復(fù)，就會發(fā)生與特定DNA聚合酶有關(guān)的一種轉(zhuǎn)移損傷DNA合稱的易錯形式，結(jié)果是一個或多個錯配堿基被摻入在損傷部分的對應(yīng)位點，most lesions in DNA are repaired by error-free di

53、rect reversal or excision repair mechanisms before passage of a replication fork. If this is not possible, an error-prone form of translesion DNA synthesis may take place involving specialized DNA ploymerases and one or more incorrect bases become incorporated opposite the lesion.Mutation: 突變，DNA堿基序

54、列水平上的永久性的、可遺傳的改變，產(chǎn)生于DNA復(fù)制或減數(shù)分裂重組過程中的自發(fā)性錯誤，或者是由于物理或化學(xué)試劑損傷DNA所致，最簡單的突變是點突變，permanent, heritable changes in te base sequence of DNA, caused by spontaneous errors in DNA replication of meiotic recombination or the damaging effects of physical or chamical agents on the DNA. Point mutation a single base c

55、hange is the simplest mutation.Mutagen: 誘變劑，通過誘導(dǎo)DNA上的突變增加突變率的物質(zhì)substitution mutation: 替換突變，分為轉(zhuǎn)換（嘌呤-嘌呤、嘧啶-嘧啶）和顛換（嘌呤-嘧啶），transition(purine-purine, pyrimidine-pyrimidine), transversion(purine-pyrimidine)deletion mutation: 缺失突變，堿基丟失，引起基因移碼突變，loss of bases and cause frameshift mutationinsertion mutation:

56、 插入突變，堿基增添，引起基因移碼突變, addition of bases and cause frameshift mutationDNA damage: DNA損傷，DNA正常的化學(xué)或物理結(jié)構(gòu)的改變，an alteration to the normal chemical or phusical srtucture of the DNADNA recombination：DNA重組，DNA分子內(nèi)或分子間發(fā)生的遺傳信息的重新共價組合過程，包括同源重組、特異位點重組和轉(zhuǎn)座重組等。同源重組：在真核生物減數(shù)分裂過程中，兩條DNA分子之間發(fā)生同源區(qū)域的交換，依靠recA，同源重組復(fù)制可使未修復(fù)損傷

57、的DNA恢復(fù)原來的完整性；位點特異性重組：發(fā)生在非同源DNA的特異片段之間的交換，不需recA或單鏈DNA；轉(zhuǎn)座作用：是較短的DNA序列，可以轉(zhuǎn)移進細(xì)胞基因組的幾乎所有位置，因不需要序列間具有同源性也不是位點特異性的而效率低。Homologous recombination: the exchange of homologous regions between two DNA moleules occurs extensively in eukaryotes during meiosis, recA-dependent. Site-specific recombination: the exc

58、hange of nonhomologous regions of DNA at specific sites is independent of recA or ssDNA. Transposition: small DNA sequences that can move to virtually any position in a cells genome, requires no homology between sequences and is not site-specific so that relatively inefficient.l Which conditions could Damage DNA and cause mutations?什么條件下可以損傷DNA而導(dǎo)致突變？化學(xué)試劑或射線，化學(xué)誘變劑（堿基類似物）可以在DNA復(fù)制過程中以錯配方式導(dǎo)