分子生物学 双语习题及精解

Section C - properties of nucleic acids1．The sequence 5'-AGTCTGACT-3' in DNA is equivalent to which sequence in RNA?A 5'-AGUCUGUGACU -3'B 5' -UGTCTGUTC -3'C 5' -UCAGUCUGA-3'D 5'- AGUCAGACU-3'2. Which of the following correctly describes A-DNA?A a right-handed antiparallel doublehelix with 10 bp/turn and bases lyingperpendicular to the helixaxis.B a left-handed antiparalleldouble-helix with 12 bp/turn formedfrom alternating pyrimidine-purinesequences.C a right-handed antiparallel doublehelix with 11 bp/turn and bases tiltedwith respect to the helix axis.D a globular structure formed by shortintramolecular helices formed in asingle-strand nucleic acid.3. Denaturation of double stranded DNA involves.A breakage into short double-stranded fragments.B separation into single strands.C hydrolysis of the DNA backbone.D cleavage of the bases from the sugar-phosphate backbone.4. Which has the highest absorption per unit mass at a wavelength of 260 nm?A double-stranded DNA.B mononucleotides.C RNA.D protein.5. Type I DNA topoisomeraes ...A change linking number by士2B require ATP.C break one strand of a DNA double helix.D are the target of antibacterial drugs. Section D - Prokaryotic and eukaryotic chromatin structure1．Which of the following is common to both E. coli and eukaryotic chromosomes?A the DNA is circular.B the DNA is packaged into nucleosomes.C the DNA is contained in the nucleus.D the DNA is negatively supercoiled.2．A complex of 166 bp of DNA with the histone octamer plus histone HI is known as a . . .A nucleosome core.B solenoid.C 30 nm fiber.D chromatosome.3．In what region of the interphase chromosome does transcription take place?A the telomere.B the centromere.C euchromatin.D heterochromatin.4．Which statement about CpG islands and methylation is not true?A CpG islands are particularly resistant to DNase I.B CpG methylation is responsible for the mutation of CpG to TpG in eukaryotes.C CpG islands occur around the promoters of active genes.D CpG methylation is associated with inactive chromatin.5．Which of the following is an example of highly-repetitive DNA?A Alu element.B histone gene cluster.C DNA minisatellites.D dispersed repetitive DNA.Section E - DNA replication1．The number of replicons in a typical mammalian cell is . . .A 40-200.B 400.C 1000-2000.D 50000-100000.2. In prokaryotes,the lagging strand primers are removed by . . .A 3' to 5' exonuclease.B DNA ligase.C DNA polymerase I.D DNA polymerase III.3. The essential initiator protein at theE. coli origin of replication is . . .A DnaA.B DnaB.C DnaC.D DnaE.4. Prokaryotic plasmids can replicate in yeast cells if they contain a cloned yeast. . .A ORC.B CDK.C ARS.D RNA.Section F - DNA damage, repair and recombination(此章不考)1. Per nucleotide incorporated, the spontaneous mutation frequency in E. coli is . . .A 1 in 106.B 1 in 108.C 1 in 109.D 1 in 1010.2. The action of hydroxyl radicals on DNA generates a significant amount of . . .A pyrimidine dimmers.B 8-oxoguanine.C O6- methylguanine.D 7-hydroxymethylguanine.3. In methyl-directed mismatchrepair in E. coli, the daughterstrand containing the mismatchedbase is nicked by . . .A M utH endonuclease.B U vrABC endonuclease.C A P endonuclease.D3' to 5' exonuclease.4. The excision repair of UV-inducedDNA damage is defective inindividuals suffering from ...A hereditary nonpolyposis colon cancer.B Crohn's disease.C classical xeroderma pigmentosum.D xeroderma pigmentosum variant. Section K - Transcription in prokaryotes1. Which two of the following statements about transcription are correct?A RNA synthesis occurs in the 3' to 5' direction.B the RNA polymerase enzyme moves along the sense strand of the DNA in a 5' to 3' direction.C the RNA polymerase enzyme movesalong the template strand of the DNA in a 5' to 3' direction.D the transcribed RNA is complementary to the template strand.E the RNA polymerase adds ribonucleotides to the 5' end of the growing RNA chain.F the RNA polymerase adds deoxyribonucleotides to the 3' end of the growing RNA chain.2. Which one of the followingstatements about E. coli RNA polymerase is false?A the holoenzyme includes the sigma factor.B the core enzyme includes the sigma factor.C it requires Mg2+ for its activity.D it requires Zn2+ for its activity.3. Which one of the following statements is incorrect?A there are two αsubunits in the E. coli RNA polymerase.B there is one β subunit in the E. coli RNA polymerase.C E. coli has one sigma factor.D the β subunit of E. coli RNA polymerase is inhibited by rifampicin.E the streptolydigins inhibit transcription elongation.F heparin is a polyanion, which binds to the β’ subunit.4. Which one of the following statements about transcription in E. coli is true?A the -10 sequence is always exactly10 bp upstream from the transcription start site.B the initiating nucleotide is always a G.C the intervening sequence between the -35 and -10 sequences is conserved.D the sequence of the DNA after thesite of transcription initiation is notimportant for transcriptionefficiency.E the distance between the -35 and -10 sequences is critical for transcription efficiency.5. Which one of the following statements about transcription in E. coli is true?A loose binding of the RNA polymerase core enzyme to DNA is non-specific and unstable.B sigma factor dramatically increasesthe relative affinity of the enzymefor correct promoter sites.C almost all RNA start sites consist of a purine residue, with A being more common than G.D all promoters are inhibited by negative supercoiling.E terminators are often A-U hairpin structures.Section L - Regulation of transcription in prokaryotes1. Which two of the following statements are correct?A the double stranded DNA sequencethat has the upper strand sequence5'-GGATCGATCC-3' is apalindrome.B the double stranded DNA sequencethat has the upper strand sequence5'-GGATCCTAGG-3' isapalindrome.C the Lac repressor inhibits binding of the polymerase to the lac promoter.D the lac operon is directly induced by lactose.E binding of Lac repressor to allolactose reduces its affinity for the lac operator.F IPTG is a natural inducer of the lac promoter.2. Which one of the following statements about catabolite-regulated operons is false?A cAMP receptor protein (CRP) andcatabolite activator protein (CAP)are different names for the sameprotein.B when glucose is present in the cell cAMP levels fall.C CRP binds to cAMP and as a result activates transcription.D CRP binds to DNA in the absence of cAMP.E CRP can bend DNA, resulting in activation of transcription.3. Which one of the following statements about the trp operon is true?A the RNA product of the trp operon is very stable.B the Trp repressor is a product of the trp operon.C the Trp repressor，like the Lac repressor, is a tetramer of identical subunits.D the Trp repressor binds totryptophan.E tryptophan activates expression from the trp operon.F the trp operon is only regulated by the Trp represso4. Which two of the following statements about attenuation at the trp operon are true?A attenuation is rho-dependent.B deletion of the attenuator sequenceresults in an increase in both basaland activated levels of tran- scriptionfrom th~ trp promoter.C the attenuator lies upstream of the trp operator sequence.D attenuation does not require tight coupling between transcription and translation.E pausing of a ribosome at twotryptophan codons in the leaderpeptide when tryptophan is in shortsupply causes attenuation.F a hairpin structure called thepnti-terminator stops formation ofthe terminator hairpin, resulting intranscriptional read-through into thetrpE gene, when tryptophan isscarce.Section M - Transcription in eukaryotes1. Which one of the followingstatements about eukaryotic RNApolymerases I, II and III is false?A RNA Pol II is very sensitive to α-amanitin.B RNA Pol II is located in th~ nucleoplasm.C RNA Pol III transcribes th~ genes for tRNA.D eukaryotic cells contain other RNApolymerases in addition to RNA PolI, RNA Pol II and RNA Pol III.E each RNA polymerase containssubunits with homology to subunitsof the E. coli RNA polymerase aswell as additional subunits，whichare unique to each polymerase.F the carboxyl end of RNA Pol IIcontains a short sequence of onlyseven amino acids which is calledthe carboxyl-terminal domain (CTD)and which may be phosphorylated.2. Which two of the following statements about RNA Pol I genes are true?A RNA Pol I transcribes the genes for ribosomal RNAs.B human cells contain 40 clusters of five copies of the rRNA gene.C the 185, 5.85 and 285 rRNAs aresynthesized as separate transcripts.D RNA Pol I transcription occurs in the nucleoplasm.E RNA Pol I transcription occurs in the cytoplasm.F rRNA gene clusters are known as nucleolar organizer regions.3. Which one of the following statements about RNA Pol I transcription is false?A in RNA Pol I promoters the coreelement is 1000 bases downstreamfrom the upstream control element(UCE).B upstream binding factor (UBF)binds to both the UCE and theupstream part of the core element ofthe RNA Pol I promoter.C selectivity factor SLl stabilizes the UBF-DNA complex.D SL1 contains several subunitsincluding the TATA-binding protein TBP.E in Acanthamoeba there is a single control element in rRNA gene promoters.4. Which two of the following statements about RNA Pol III genes are true?A the transcriptional control regions of tRNA genes lie upstream of the start of transcription.B highly conserved sequences in tRNA gene coding regions are also promoter sequences.C TFIIIC contains TBP as one of its subunits.D TFIIIB is a sequence specific transcription factor on its own.E in humans 5S rRNA genes are arranged in a single cluster of 2000 copies.Section 0 - RNA processing and RNPs 1. Which ribonucleases are involved in producing mature tRNA in E. coli?A RNases A, D, E and F.B RNases D, E, F and H.C RNases D, E, F and P.D RNases A, D, H and P.2. Most eukaryotic pre-mRNAs arematured by which of the followingmodifications to their ends?A capping at the 3’-end cleavage and polyadenylation at the 5'-end.B addition of a GMP to the 5'-end，cleavage and polyadenylation to create the 3'-end.C addition of a guanine residue to the5'-end cleavage and polyadenylationto create the 3'-end.D addition of a GMP to the 5'-end，polyadenylation，then cleavage to create the 3'-end.3. Which one of the followingstatements correctly describes thesplicing process undergone bymost eukaryotic pre-mRNAs?A in a two-step reaction, thespliceosome removes the exon as alariat and joins the two intronstogether.B splicing requires conservedsequences which are the 5ιsplicesite，the 3' -splice site thebranch-point and the polypurinetract.C the U1 snRNP initially binds to the5'-splice site，U2 to the branchpointsequence and then the tri-snRNP, U4,US and U6 can bind.D in the first step of splicing the G atthe 3'-end of the intron is joined tothe 2’-hydroxyl group of the Aresidue of the branchpoint sequenceto create a lariat.Section P - The genetic code and tRNA 1. Which of the following list of features correctly apply to the genetic code?A triplet degenerate nearly universal, comma-less, nonoverlapping.B triplet universal, comma-less, degenerate, nonoverlapping.C overlapping, triplet, comma-less, degenerate nearly universal.D overlapping, comma-less nondegenerate nearly universal triplet. 2. Which of the following statementsabout tRNAs is false?A most tRNAs are about 76 residues long and have CCA as residues 74, 75 and 76.B many tRNAs contain the modifiednucleosides pseudouridinedihydrouridine ribothymidine andmosme.C tRNAs have a common L-shapedtertiary structure with threenucleotides at one end able to basepair with an anticodon on amessenger RNA molecule.D tRNAs have a common cloverleafsecondary structure containing threesingle stranded loops called the D-,T- and anticodon loops.3．Which three statements are true? The aminoacyl tRNA synthetase reaction...A joins AMP to the 3’-end of the tRNA.B is a two step reaction.C joins any amino acid to the 2'- or 3' -hydroxyl of the ribose of residue A76.D is highly specific because thesynthetases use identity elements inthe tRNAs to distinguish betweenthem.E joins AMP to the amino acid to produce an intermediate.F releases PPi in the second step. Section Q - Protein synthesis1. Which statement about the codon-anticodon interaction is false?A it is antiparallel and can include nonstandard base pairs.B inosine in the 5' -anticodon position can pair with A,C or U in the 3'-codonpositionC inosine in the 3’-anticodon position can pair with A, C or U in the 5’-codon position.D A is never found in the 5'-anticodon position as it is modified by anticodon deaminase.2．Which one of the following statements correctly describes initiation of protein synthesis in E.coli?A the initiator tRNA binds to the Shine-Dalgarno sequence.B three initiation factors are involved and IF2 binds to GTP.C the intermediate containing IF1, IF2,IF3, initiator tRNA and mRNA is called the 30S initiation complex.D binding of the 50S subunit releases IF1, IF2, GMP and PPi.E the initiation process is completewhen the 70S initiation complex is formed which contains the initiator tRNA in the A site of the ribosome and an empty P site.3．Which statement about elongation of protein synthesis in prokaryotes is false?A elongation can be divided into threesteps: peptidyl-tRNA deliverypeptide bond formation andtranslocation.B the peptidyl transferase center of thelarge ribosomal subunit isresponsible for peptide bond for-mation.C in the EF-Tu-Ts exchange cycleEF-Tu-GTP is regenerated by EF-Tsdisplacing GDP.D EF-G is also known as translocaseand uses GTP in its reaction.4．Which two of the following statements about initiation ofeukaryotic protein synthesis aretrue?A eukaryotes use a mRNA scanning method to locate the correct start codon.B there are at least nine eukaryotic initiation factors (eIFs).C eukaryotic initiation uses N-formylmethionine.D the 80S initiation complexcompletes the initiation process andcontains the initiator tRNA base-paired to the start codon in the Asite.E ATP is hydrolysed to AMP and PPi during the scanning process.F the initiator tRNA binds after the mRNA has bound to the small subunit.。