《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》由会员分享，可在线阅读，更多相关《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（7页珍藏版）》请在三一文库上搜索。
1、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 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A 试卷 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 each) Your answer should describe what each item is and how it functions in the cell
2、. Diagrams, structure and sequence information could be included in your answer, as necessary. 1. Trombone model 2. TFIID 3. Telomerase 4. RNA editing 5. Tandem mass spectrometry 6. tRNA synthetase 7. Viral-like retrotransposons 8. Transcriptional silencing 9. Suppression mutation 10. Shine-Dalgarno
3、 sequence PART II: MULTIPLE/SINGLE CHOICES (2 points each) 1. The following molecule is _ 1) 2-deoxyadenosine 5-phosphate 2) 2-deoxyadenosine 3) dAMP 4) dATP 2. The strictness of the rules for “ Waston-Crick”pairing derives from the complementarities_ between adenine and thymine and between guanine
4、and cytosine. 1) of base stacking 2) of shape 3) of hydrogen bonding properties 4) of size 3. Which of the following statements correctly describe the difference between DNA and RNA? _ 1) The major groove of the regular DNA double helical structure is rich in chemical information. 2) RNA contains de
5、oxyribose 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 chromosomes, which of the following statements are CORRECT in describing the structure and
6、 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 interaction of DNA with the histone octamer is very stable and cannot be altere
7、d unless during DNA replication. 4) Nucleosome remodeling by the action of enzymes such as histone acetylase is very important for gene expression. 5. Which of the following statements regarding genomes of living organism is NOT correct? _ 1) Genome size is roughly related to the complexity of the o
8、rganism. 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. 6. The fact that most amino acids are specified by multi
9、ple 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 DNA with a double-stranded break? 1) Base
10、 excision repair 2) Nucleotide excision repair 3) Translesion repair 4) RecBCD pathway repair 5) Mismatch repair 8. Which of the following factors/elements regarding translation are CORRECT? 1) Ribosome binding site (RBS) is essential for the translation initiation in bacterial and eukaryotic cells.
11、 2) The polyA tail in the 3 end of an mRNA promotes the efficient recycling of ribosomes, 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 displace the tRNA
12、 bound to the A site. 5) The ribosome is a ribozyme because the large rRNA is responsible for the peptidyl transferase 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) Transcr
13、iption 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 library 2) Obtain a cDNA library 3) Shotgun sequencing on automated sequencers 4) Sequence assembly on comp
14、uters 5) BLAST search 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 describe his/her research achievement and contribution to the molecular biology knowledge that you ve l
15、earned 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 and spliceosome-mediated pre-mRNA splicing. 4. What are the general principles of trans
16、cription regulation in both prokaryotic and eukaryotic cells? 5. Please give an example to demonstrate that the RNA secondary structure can regulate gene expression in bacteria. Example 1: The attenuation regulation of the tryptophan operon. Example 2: Ribo-switch regulation 6. How the activators an
17、d repressors regulate gene expression in eukaryotic cells? 7. The following DNA sequence contains a small open reading frame (ORF) which encodes only 5 amino acids. Please list the 5 genetic codons and the stop codon of the ORF. Which strand of the DNA (upper or lower strand) is the template for RNA
18、 transcription? The promoter of the gene is in the right or left side of the sequence? 5 TCATGCTAGACACGTAATAGCATATGGGA 3 3 AGTACGATCTGTGCATTATCGTATACCCT 5 PART IV: MAJOR QUESTIONS (10 points each, total of 30 points) 1. Please discuss what you have learned from this course, including (1) the general
19、 knowledge framework, (2) your most interested knowledge and why this knowledge has impressed you, (3) the value of teamwork, (4) any change of your learning attitude and/or the construction of your interest in science. 2. Please discuss the similarity and difference between miRNA and siRNA, and des
20、cribe the distinct contributions of these two small regulatory RNAs to the fundamental biology and application, respectively. 3. It has been recently reported that a new protein X functions in repressing the transcription of an oncogene gene Y. Could you design experiments to test if X protein binds
21、 to the promoter region of Y gene (1) in vitro and (2) in vivo? If it does bind, could you design an experiment to test if the binding is essential for the transcriptional repression? Notes: You have all DNA sequences, plasmid vectors, cloning enzymes and other reagents that he needs. 答案 PART I: 1.
22、Trombone model This model is proposed to explain the coordinated synthesis of the leading strand and the lagging strand to the direction of the replication folk movement at a replication folk (2 ) 2. TFD A transcription factor composed of TBP and TAFs for RNA polymerase;(1 ) TBP recognizes TATA box
23、and TBP-DNA complex provides a platform for other transcription factors and polymerase to the promoter;(1) Two of TAFs bind the core promoter elements such as Inr and DPE. Several of histone-like TAFs are also associated with some histone modification enzymes.(1) 3. Telomerase: Solve the End Replica
24、tion Problem (1) through adding the telomeric sequence to 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-specific deamination of insertion.(1) 5. Tandem mass spectrometry Answer 1: A method that
25、determines the protein sequence based on the accurate mass of protein fragments obtained by mass spectrometry (2) Answer 2: (2) 6.Aminoacyl tRNA synthetase An enzyme that catalyzes the attachment of an amino acid to a cognate tRNA (2 ) through two steps: adenylylation of amino acid and tRNA charging
26、 (+1) 7. Viral-like retrotransposons: also called long terminal reapeat (LTR) retrotransposons. The element includes two long terminal repeat sequences that flank a region encoding two enzymes: integrase and reverse transcriptase. It mediate transposition reaction through a RNA intermediate. 8 Trans
27、criptional silencing is a specialized form of repression that can spread along chromatin,(1) switching off multiple genes without the need for each to bear binding sites for specific repressors(1). The mechanism of this repression is the propagation of certain repressing histone modifications over s
28、tretches of chromatin. (1) Insolator elements can block this spreading, thus protect some inserted gene from silencing.(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 diffe
29、rent gene (intergenetic) or on the same gene (intragenetic) 10. Shine-Dalgarno sequence: 又称 RBS, ribosome binding site Key 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 complim
30、ented to certain region of 16s rRNA (2) the conservation and spacing decides the activeness of the following OFR Part III: Short questions 2 Each mRNA gene contains a poly-A signal sequence near the termination site(1). Eukaryotic transcription termination is highly coupled with polyadenylation:(1)
31、(1) CstF/CPSF bound at the CTD tail is transferred to poly-A signal sequence after ti is transcripted, resulting in mRNA cleavage and recruitment of enzymes for polyadenylation .(2) (2) Poly-A polynerase(PAP) adds about 200 As to RNAs 3 end.(2) Two models for polymerase recycle: (3) Transfer of 3 -p
32、rocessing enzymes from CTD tail to RNA triggers comformational change in Pol, reduce processivity, leading to spontaneous termination.(0.5) (4) Absense of 5-cap is sensed by the Pol, recognizes the transcript as improper and terminates.(0.5) 3.Please describe the similarity and difference between gr
33、oup II intron and spliceosome-mediated pre-mRNA splicing.(答案有点长，大家可以在精简一下。) Spliceosome-mediated splicing of mRNA (6) Chemistry (2): splicing occurs as two sequential ester-transfer reactions. Firstly, the 2 OH of the branch point A attacks the phosphoryl group of a conserved 5 G at he 5 splice site
34、, resulting in the free of 5 exon from the intron. Then, the 3 OH of the free 3 end of 5 exon attacks a phosphoryl group at the 3 splice site, resulting in the ligation 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 recogni
35、tion of the 5 splice site, 3 splice site and 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. The base-pairing between U2 snRNA with the branch site make the conserved A residue in the branch site extruded from the paired
36、 region, and thus this A is ready to carry the nucleophile attack. The tri-snRNP U4/U6/U5 joins and A complex is arranged to B complex in which the three splice sites are brought together. In this complex U4/U6 snRNPs are held together tightly by extensive base-pairing between U4 and U6 snRNAs. Step
37、 3, U1 leaves the complex, and U6 occupies the 5 splice site by base-pairing. U4 leaves the complex, allowing the RNA components of U2 and U6 to base pair to produce the active site. The branch site A attacks the 5 splice site, forming the 3-way junction and C complex. The 5 splice site then attacks
38、 the 3 splice site, freeing the intron lariat and forming the mRNA product. Group intron splicing (2) : the chemistry and the RNA intermediates produced are the same as that of the spliceosome-mediated mRNA splicing, but the splicing is catalyzed by the intron RNA itself, which is also named as self
39、-splicing. The intron itself folds into a specific conformation and catalyzed the chemistry of its own release. 4.What are the general principles of transcription of regulation in both prokaryotic and eukaryotic cells? Both regulations are mediated by regulatory proteins: activators and repressors;
40、(1.5) Activators act using both recruitment and allostery. (1.5) Both regulations are controlled at different stages: the initiation is the pervasively regulated step, also involves regulation after initiation (2) Both regulations act at a distance and involve DNA looping. (+0.5) Both regulations in
41、volve cooperative binding. (+0.5) 5. Example 1.Attenuation of trp operon (1) the 4 regions of the leader RNA could form 3 kinds of possible hairpin loop: region 1 with region 2, region 2 with region 3, region 3 with region 4, ( region 1: two trp codons) (2) transcription right side PART IV: 1. omitt
42、ed 2. Please discuss the similarity and difference between miRNA and siRNA, and describe the distinct contribution of these two small regulatory RNAs to the fundamental biology and application, respectively. Answer: Similarity: (4) 1. Structural: Both are about 20-23 nt consist of sense and antisens
43、e strand (1) 2. Biogenesis: Both are cleaved from precursor by Dicer (1) 3. Function: one strand is incorporated into RISC complex and complement with target mRNA (1) 4. Result: Both could cause gene silencing. (1) Difference (2): Biogenesis: miRNA is endogenously and encoded and siRNA is exogenousl
44、y and artificial prepared; (1) miRNA is produced from pri-miRNA to pre-miRNA to mature miRNA, pre-miRNA is stem-loop RNA, but siRNA is directly cleaved from long dsRNA (1) Contribution (4) MiRNA: miRNA is phylogenetically conserved regulatory RNAs playing diverse and critical functions in cell proli
45、feration and differentiation, and development (2) SiRNA: siRNA has significantly contributed to silencing gene function (1) and representing a therapeutic approach to combat disease and viral infection. (1) 3. (1) To test if X binds to the Y gene promoter in vitro: One of the effective ways is elect
46、rophoretic mobility shift assay (EMSA) or called gel-shift assay. Y gene fragment is amplified using PCR (e.g. from genomic DNA). Get radioactive isotope to label this fragment so as to track it in following steps; The fragment corresponding to protein X is obtained the same way, and cloned into an
47、expression vector. Use E. coli to express protein X, and purify it; Y gene fragment and protein X are mixed under appropriate condition to let them bind together. The sample is then loaded onto native PAGE and run. The change of the electrophoretic mobility of DNA, caused by protein binding, is mani
48、fested in the position shift on the gel. X-ray film or phosphor screen is needed to show the result. (2) To test if X binds to the Y gene promoter in vivo: using chromatin immunoprecipitation (ChIP). Add formaldehyde to cells to cross-link DNA and the binding protein; Lyse the cells and break DNA into small fragments; Use beads attached to the specific antibody of protein X to drag down the complex containing X and the bound DNA fragment; Remove protein X and use primers specific to Y gene promoter to test whethe