武汉大学生命科学学院2007至2008学年第一学期分子生物学期末考试试题A.pdf

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1、武汉大学生命科学学院武汉大学生命科学学院 20072007 至至 20082008 学年第一学期分子生物学期末考试试题学年第一学期分子生物学期末考试试题 A A武汉大学生命科学学院20072008 学年第一学期期末考试分子生物学分子生物学A A 试卷试卷Final exam of Molecular Biology Course(Fall 2007)Final exam of Molecular Biology Course(Fall 2007)年级(Grade)_专业(Major)_姓名 Name _学号(Student ID)_PART I:DESCRIPTION(2 points eac

2、h)PART I:DESCRIPTION(2 points each)Your answer should describe what each item is and how it functions in the cell.Diagrams,structureand sequence information could be included in your answer,as necessary.1.Trombone model2.TFIID3.Telomerase4.RNA editing5.Tandem mass spectrometry6.tRNA synthetase7.Vira

3、l-like retrotransposons8.Transcriptional silencing9.Suppression mutation10.Shine-Dalgarno sequencePART II:MULTIPLE/SINGLE CHOICES(2 points each)PART II:MULTIPLE/SINGLE CHOICES(2 points each)1.The following molecule is _1)2-deoxyadenosine 5-phosphate2)2-deoxyadenosine3)dAMP4)dATP2.Thestrictnessofther

4、ulesfor“Waston-Crick”pairingderivesfromthecomplementarities_ between adenine and thymine and between guanine and cytosine.1)of base stacking2)of shape3)of hydrogen bonding properties4)of size3.Which of the following statements correctly describe the difference between DNA and RNA?_1)The major groove

5、 of the regular DNA double helical structure is rich in chemicalinformation.2)RNA contains deoxyribose and uracil.3)All RNAs are single-stranded while DNA is double-stranded.4)Some RNAs can fold up into complex tertiary structures,and function as enzymes.4.Nucleosomes are the building blocks of chro

6、mosomes,which of the following statementsare CORRECT in describing the structure and function of nucleosome?_1)The nucleosome is composed of a core containing eight histone proteins and the DNA(147 bp)wrapped around them.2)The core histones specifically contact the major groove of the DNA.3)The inte

7、raction of DNA with the histone octamer is very stable and cannot be alteredunless during DNA replication.4)Nucleosome remodeling by the action of enzymes such as histone acetylase is veryimportant for gene expression.5.Which of the following statements regarding genomes of living organism is NOT co

8、rrect?_1)Genome size is roughly related to the complexity of the organism.2)The number of genes in a genome cannot explain the complexity of the organism.3)The average number of introns per gene increases with the organism complexity.4)The gene density(genes/Mb)increases with the organism complexity

9、.6.The fact that most amino acids are specified by multiple codons is known as:_1)The“wobble”phenomenon.2)The universality of the genetic code.3)Codon bias.4)The anticodon hypothesis.5)The redundancy of the genetic code.7.Which of the following repair mechanisms is involved in repair of the damaged

10、DNA with adouble-stranded break?1)Base excision repair2)Nucleotide excision repair3)Translesion repair4)RecBCD pathway repair5)Mismatch repair8.Which of the following factors/elements regarding translation are CORRECT?1)Ribosome binding site(RBS)is essential for the translation initiation inbacteria

11、l and eukaryotic cells.2)The polyA tail in the 3 end of an mRNA promotes the efficient recycling ofribosomes,and therefore the translational efficiency.3)Ribosome is able to discriminate between correctly or incorrectly charged tRNAs.4)The translocation factor EF-G mimics a tRNA molecule so as to di

12、splace the tRNAbound to the A site.5)The ribosome is a ribozyme because the large rRNA is responsible for the peptidyltransferase activity.9.RNA polymerase III is the eukaryotic enzyme responsible for:1)Transcription of ribosomal RNA.2)Transcription of transfer RNA and other small RNA species.3)Tran

13、scription of messenger RNA.4)Initiation of Okazaki fragment synthesis in DNA replication.10 To obtain the sequence of a genome,which of the following steps are required?_1)Obtain a genomic library2)Obtain a cDNA library3)Shotgun sequencing on automated sequencers4)Sequence assembly on computers5)BLA

14、ST searchPART III:SHORT QUESTIONS(CHOOSE SIX QUESTIONS TO ANSWER)(5 points each,total of 30 points)PART III:SHORT QUESTIONS(CHOOSE SIX QUESTIONS TO ANSWER)(5 points each,total of 30 points)1.Who is your favorite scientist among those introduced in this course?Please describehis/her research achievem

15、ent and contribution to the molecular biology knowledge that youve learned and how his/her experience influences your research attitude.2.How the transcription of an mRNA is terminated in eukaryotic cells?3.Please describe the similarity and difference between group II intron andspliceosome-mediated

16、 pre-mRNA splicing.4.What are the general principles of transcription regulation in both prokaryotic andeukaryotic cells?5.Please give an example to demonstrate that the RNA secondary structure can regulate geneexpression in bacteria.Example 1:The attenuation regulation of the tryptophan operon.Exam

17、ple 2:Ribo-switch regulation6.How the activators and repressors regulate gene expression in eukaryotic cells?7.The following DNA sequence contains a small open reading frame(ORF)which encodes only5 amino acids.Please list the 5 genetic codons and the stop codon of the ORF.Which strandof the DNA(uppe

18、r or lower strand)is the template for RNA transcription?The promoter ofthe gene is in the right or left side of the sequence?5 TCATGCTAGACACGTAATAGCATATGGGA 33 AGTACGATCTGTGCATTATCGTATACCCT 5PART IV:MAJOR QUESTIONS(10 points each,total of 30 points)PART IV:MAJOR QUESTIONS(10 points each,total of 30

19、points)1.1.Please discuss what you have learned from this course,including(1)the generalknowledge framework,(2)your most interested knowledge and why this knowledge has impressedyou,(3)the value of teamwork,(4)any change of your learning attitude and/or theconstruction of your interest in science.2.

20、2.Please discuss the similarity and difference between miRNA and siRNA,and describe thedistinct contributions of these two small regulatory RNAs to the fundamental biology andapplication,respectively.3.3.It has been recently reported that a new protein X functions in repressing thetranscription of a

21、n oncogene gene Y.Could you design experiments to test if X protein bindsto the promoter region of Y gene(1)in vitro and(2)in vivo?If it does bind,could youdesign an experiment to test if the binding is essential for the transcriptional repression?Notes:You have all DNA sequences,plasmid vectors,clo

22、ning enzymes and other reagents thathe needs.答案答案PART I:1.Trombone modelThis model is proposed to explain the coordinated synthesis of the leading strand and thelagging strand to the direction of the replication folk movement at a replication folk(2)2.TFDA transcription factor composed of TBP and TA

23、Fs for RNA polymerase;(1)TBP recognizes TATA box and TBP-DNA complex provides a platform for other transcriptionfactors and polymerase to the promoter;(1)Two of TAFs bind the core promoter elements such as Inr and DPE.Several of histone-like TAFsare also associated with some histone modification enz

24、ymes.(1)3.Telomerase:Solve the End Replication Problem(1)through adding the telomeric sequenceto the 3end of the telomere.(1)No extra primer nor template needed.4.RNA editing:a way of changing the sequence of RNA after transcription(1)by site-specificdeamination of insertion.(1)5.Tandem mass spectro

25、metryAnswer 1:A method that determines the protein sequence based on the accurate mass of proteinfragments obtained by mass spectrometry (2)Answer 2:(2)6.Aminoacyl tRNA synthetaseAn enzyme that catalyzes the attachment of an amino acid to a cognate tRNA(2)through two steps:adenylylation of amino aci

26、d and tRNA charging(+1)7.Viral-like retrotransposons:also called long terminal reapeat(LTR)retrotransposons.Theelement includes two long terminal repeat sequences that flank a region encoding two enzymes:integrase and reverse transcriptase.It mediate transposition reaction through a RNAintermediate.

27、8 Transcriptional silencing is a specialized form of repression that can spread alongchromatin,(1)switching off multiple genes without the need for each to bear binding sitesfor specific repressors(1).The mechanism of this repression is the propagation of certainrepressing histone modifications over

28、 stretches of chromatin.(1)Insolator elements can block this spreading,thus protect some inserted gene fromsilencing.(0.5)9.Suppressor Mutation:抑制突变，抑制基因突变，抑制因子突变Key points:(1)a second mutation(2)the GENOTYPE is mutationally altered but the wild type PHENOTYPE restores(1)maybe on a different gene(in

29、tergenetic)or on the same gene(intragenetic)10.Shine-Dalgarno sequence:又称 RBS,ribosome binding siteKey points:(1)in prokaryotic cells(2)a stretch of RNA 3 to 9 nucleosides upstream of the start codon in a mRNA(3)contains conservative sequence:5-AGGAGG-3,which is complimented to certain regionof 16s

30、rRNA(2)the conservation and spacing decides the activeness of the following OFRPart III:Short questions2 Each mRNA gene contains a poly-A signal sequence near the termination site(1).Eukaryotic transcription termination is highly coupled with polyadenylation:(1)(1)CstF/CPSF bound at the CTD tail is

31、transferred to poly-A signal sequence after tiis transcripted,resulting in mRNA cleavage and recruitment of enzymes forpolyadenylation.(2)(2)Poly-A polynerase(PAP)adds about 200 As to RNAs 3 end.(2)Two models for polymerase recycle:(3)Transfer of 3-processing enzymes from CTD tail to RNA triggers co

32、mformational changein Pol,reduce processivity,leading to spontaneous termination.(0.5)(4)Absense of 5-cap is sensed by the Pol,recognizes the transcript as improper andterminates.(0.5)3.Please describe the similarity and difference between group II intron and spliceosome-mediatedpre-mRNA splicing.(答

33、案有点长，大家可以在精简一下。)Spliceosome-mediated splicing of mRNA(6Spliceosome-mediated splicing of mRNA(6)Chemistry(2):splicing occurs as two sequential ester-transfer reactions.Firstly,the 2OH of the branch point A attacks the phosphoryl group of a conserved 5 G at he5 splice site,resulting in the free of 5 e

34、xon from the intron.Then,the 3 OH of thefree 3 end of 5 exon attacks a phosphoryl group at the 3 splice site,resulting in theligation of the 5 and 3 exons and release of a lariat form of intron.Mechanisms(4):Step 1,formation of the E(early)complex by recognition of the 5 splice site,3splice site and

35、 A branch point by U1 snRNP,U2AF and BBP respectively.Step 2,U2 snRNP bind to the branch site to replace BBP forms A complex.Thebase-pairing between U2 snRNA with the branch site make the conserved A residue inthe branch site extruded from the paired region,and thus this A is ready to carry thenucle

36、ophile attack.The tri-snRNP U4/U6/U5 joins and A complex is arranged to Bcomplex in which the three splice sites are brought together.In this complex U4/U6snRNPs are held together tightly by extensive base-pairing between U4 and U6snRNAs.Step 3,U1 leaves the complex,and U6 occupies the 5 splice site

37、 by base-pairing.U4 leaves the complex,allowing the RNA components of U2 and U6 to base pair toproduce the active site.The branch site A attacks the 5 splice site,forming the 3-wayjunction and C complex.The 5 splice site then attacks the 3 splice site,freeing theintron lariat and forming the mRNA pr

38、oduct.GroupGroup intron splicing(2intron splicing(2):the chemistry and the RNA intermediates produced are the same asthat of the spliceosome-mediated mRNA splicing,but the splicing is catalyzed by the intronRNA itself,which is also named as self-splicing.The intron itself folds into a specificconfor

39、mation and catalyzed the chemistry of its own release.4.What are the general principles of transcription of regulation in both prokaryotic andeukaryotic cells?Both regulations are mediated by regulatory proteins:activators and repressors;(1.5)Activators act using both recruitment and allostery.(1.5)

40、Both regulations are controlled at different stages:the initiation is the pervasively regulatedstep,also involves regulation after initiation(2)Both regulations act at a distance and involve DNA looping.(+0.5)Both regulations involve cooperative binding.(+0.5)5.Example 1.Attenuation of trp operon(1)

41、the 4 regions of the leader RNA could form 3 kinds of possible hairpin loop:region 1 withregion 2,region 2 with region 3,region 3 with region 4,(region 1:two trp codons)(2)transcription&translation in prokaryotic cells are coupled.(3)When the level of tryptophan is moderate,the ribosome“stop”on the

42、region 1&2 whenregion 3&4 are transcribed.So,region 3 pair with region 4 to form a hairpin resulting inthe termination of the transcription.(4)When the level of tryptophan is low enough,the ribosome stalls at the two adjacent trpcodens,leaving region 2 pairs with region 3,thereby preventing the form

43、ation of terminationhairpin.Thus the operon could be transcribed and then translated.Example 2 Riboswitches(1)riboswitches are regulatory RNA elements that sensors the small metabolites to controlgene transcription&translation.Two types:(1)when it binds no metabolites,the anti-terminator is formed i

44、n the 5-UTR of mRNA therebythe transcription is turned on(2)when it binds to certain metabolites,a terminator forms and the transcription is turnedoff.(1)when is binds no metabolites,the RBS is exposed to ribosome so that the translation isaccomplished.(2)When it binds certain metabolites,the RBS is

45、 sequestered by the resulting secondarystructure,preventing the translation of the mRNA.6 How the activators and repressors regulate gene expression in eukaryotic cells?(5)Activators:a.recruiting the transcriptional machinery to the gene (1)b.recruiting nucleosomemodifiers (1)Repressors:(Competition

46、)(Inhibition)(Direct repression)(Indirect repression)a.Competition:competing for the binding site of activators (1)b.Inhibition:inhibiting the function of theactivator.(1)c.Direct repression:interacting directly with the transcriptional machinery atthe the promoter and inhibiting transcription.d.Ind

47、irect repression:recruiting nucleosome modifiers(most common)(1)7Five codons:AUG,CUA,UUA,CGU,GUC stop codon is UAG upper strand;right sidePART IV:1.omitted2.Please discuss the similarity and difference between miRNA and siRNA,and describe the distinctcontribution of these two small regulatory RNAs t

48、o the fundamental biology and application,respectively.Answer:Similarity:(4)1.Structural:Both are about 20-23 nt consist of sense and antisense strand(1)2.Biogenesis:Both are cleaved from precursor by Dicer(1)3.Function:one strand is incorporated into RISC complex and complement with targetmRNA(1)4.

49、Result:Both could cause gene silencing.(1)Difference(2):Biogenesis:miRNA is endogenously and encoded and siRNA is exogenously and artificialprepared;(1)miRNA is produced from pri-miRNA to pre-miRNA to mature miRNA,pre-miRNAis stem-loop RNA,but siRNA is directly cleaved from long dsRNA(1)Contribution

50、(4)MiRNA:miRNA is phylogenetically conserved regulatory RNAs playing diverse and critical functionsin cell proliferation and differentiation,and development(2)SiRNA:siRNA has significantly contributed to silencing gene function(1)and representing atherapeutic approach to combat disease and viral inf