分子生物学 双语习题及精解

Section C - properties of nucleic acids

1．The sequence 5'-AGTCTGACT-3' in DNA is equivalent to which sequence in RNA?

A 5'-AGUCUGUGACU -3'

B 5' -UGTCTGUT

C -3'

C 5' -UCAGUCUGA-3'

D 5'- AGUCAGACU-3'

2. Which of the following correctly describes A-DNA?

A a right-handed antiparallel double

helix with 10 bp/turn and bases lying

perpendicular to the helix

axis.

B a left-handed antiparallel

double-helix with 12 bp/turn formed

from alternating pyrimidine-purine

sequences.

C a right-handed antiparallel double

helix with 11 bp/turn and bases tilted

with respect to the helix axis.

D a globular structure formed by short

intramolecular helices formed in a

single-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2

B require ATP.

C break one strand of a DNA double helix.

D are the target of antibacterial drugs. Section D - Prokaryotic and eukaryotic chromatin structure

1．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 replication

1．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 the

E. 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 mismatch

repair in E. coli, the daughter

strand containing the mismatched

base is nicked by . . .

A M utH endonuclease.

B U vrAB

C endonuclease.

C A P endonuclease.

D3' to 5' exonuclease.

4. The excision repair of UV-induced

DNA damage is defective in

individuals suffering from ...

A hereditary nonpolyposis colon cancer.

B Crohn's disease.

C classical xeroderma pigmentosum.

D xeroderma pigmentosum variant. Section K - Transcription in prokaryotes

1. 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 moves

along 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 following

statements 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 exactly

10 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 the

site of transcription initiation is not

important for transcription

efficiency.

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 increases

the relative affinity of the enzyme

for 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 prokaryotes

1. Which two of the following statements are correct?

A the double stranded DNA sequence

that has the upper strand sequence

5'-GGATCGATCC-3' is a

palindrome.

B the double stranded DNA sequence

that has the upper strand sequence

5'-GGATCCTAGG-3' is

apalindrome.

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 IPT

G 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) and

catabolite activator protein (CAP)

are different names for the same

protein.

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 to

tryptophan.

E tryptophan activates expression from the trp operon.

F the trp operon is only regulated by the Trp represso

4. Which two of the following statements about attenuation at the trp operon are true?

A attenuation is rho-dependent.

B deletion of the attenuator sequence

results in an increase in both basal

and activated levels of tran- scription

from 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 two

tryptophan codons in the leader

peptide when tryptophan is in short

supply causes attenuation.

F a hairpin structure called the

pnti-terminator stops formation of

the terminator hairpin, resulting in

transcriptional read-through into the

trpE gene, when tryptophan is

scarce.

Section M - Transcription in eukaryotes

1. Which one of the following

statements about eukaryotic RNA

polymerases 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 RNA

polymerases in addition to RNA Pol

I, RNA Pol II and RNA Pol III.

E each RNA polymerase contains

subunits with homology to subunits

of the E. coli RNA polymerase as

well as additional subunits，which

are unique to each polymerase.

F the carboxyl end of RNA Pol II

contains a short sequence of only

seven amino acids which is called

the 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 are

synthesized 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 core

element is 1000 bases downstream

from the upstream control element

(UCE).

B upstream binding factor (UBF)

binds to both the UCE and the

upstream part of the core element of

the RNA Pol I promoter.

C selectivity factor SLl stabilizes the UBF-DNA complex.

D SL1 contains several subunits

including 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 are

matured by which of the following

modifications 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 the

5'-end cleavage and polyadenylation

to create the 3'-end.

D addition of a GMP to the 5'-end，