暨南分子生物学期末选择题

Multiple choice: Macromolecules:

1. The polarity （极性）of DNA chain is represented by ___ _A _ (a) 3’-5’; (b)1’-6’; (c) 1’-3’; (d) 2’-3’; (e) none of the above.

2. The kind of nucleic acid that is represented by a cloverleaf（三叶草结构）model is ___ _D _ (a) mitochondrial DNA;. (b) chromosomal DNA; (c)rRNA; (d)tRNA; (e)mRNA. 3. Which histone protein is not part of a nucleosome（核小体）? ___ _A _ (a) H1; (b) H2a; (c) H2b; (d) H3; (e) H4.

4. The backbone（骨架） of a DNA molecule is ___ _D _ a. made up of sugars

b. made up of nitrogenous bases c. made up of phosphate groups

d. made up of alternating phosphate and sugar groups e. made up of alternating sugars and nitrogenous base

5. Supercoiling（超螺旋） in linear DNA has what advantage（优点） for the eukaryotic cell? ___ _E _ a. It helps to compact DNA so that it fits into the nucleus.

b. It helps to expand DNA so that it is more accessible to metabolic enzymes.

c. Underwound DNA exerts a force that helps separate the two strands of DNA during transcription. d. Overwound DNA exerts a force that helps separate the two strands of DNA during transcription. e. a and

Genes and genome:

1. All of the following are features of eukaryotic（真核） but not prokaryotic（原核） genetic systems EXCEPT ___ _A _ (a) Transcription and translation are coupled; (b) Export of spliced mRNAs; (c) Only monocistronic mRNAs; (d) \ (e) Compartmentalization

2.The term genome refers to ___ _A _ (a) The complete set of genetic information that an organism has; (b) It is another word for bacterial chromosome;

(c) A pair of identical chromosomes from a eukaryotic cell; (d) The complete DNA sequence of a chromosome; (e) A gene plus the regulatory region in front of it.

3.Which of the following statements is FALSE regarding eukaryotic chromosomes? ___ _A _ (a) Because they are larger than prokaryotic chromosomes and have a single ori, replication in eukaryotes is much faster than in prokaryotes;

(b) They are linear with a centromere and two telomeres;

(c) They are larger and contain many more genes than prokaryotic chromosomes; (d) They contain many repetitive sequences;

(e) Because they contain genes with introns, the DNA of a gene is actually much longer than the mature mRNA that is produced from that gene.

1

DNA replication:

1. All replicons must ___ _D _ (a) be contained within the nucleus; (b) be composed of circular DNA or RNA; (c) be composed of DNA; (d) have an origin of replication; (e) carry a gene for DNA polymerase

2. SSB（单链结合蛋白）protein ___ _D _ (a) unwinds the double helix in front of the replication fork;

(b) attaches the synthetic subunit of DNA polymerase to the DNA; (c) inserts the primer for DNA synthesis;

(d) keeps the DNA single stranded at the replication fork; (e) seals the nicks between Okazaki fragments.

3. During rolling circle replication（滚环复制） ___ _C _ (a) Many interlocking circles of DNA are made; (b) Two origins of replication are used;

(c) A single strand is nicked when replication starts; (d) A circular RNA primer is used; (e) None of the above is true.

4. During rolling circle replication, which of the following is false? ___ _C _ (a) There is no RNA primer synthesis required for synthesis of the leading strand.

(b) The leading strand is covalently linked to the parental template used for lagging strand synthesis. (c) No lagging strand is synthesized.

(d) The template used for synthesis of the lagging strand remains intact.

5. Telomerase（端粒酶）is a ribonucleoprotein（核糖核蛋白）complex that___ _C _ (a) synthesizes DNA in the absence of a DNA or RNA template.

(b) synthesizes DNA use a DNA template that is part of the ribonucleoprotein complex. (c) synthesizes DNA use a RNA template that is part of the ribonucleoprotein complex. (d) synthesizes DNA using ribosomal RNA as template.

6. Telomeres are shortened slightly after every round of replication because ___ _B _ (a) Telomerase cuts off several 6-bp repeats.

(b) The gap created by removal of the RNA primer at the very end of the chromosome cannot be filled in (c) The gap created by removal of the RNA primer in the center of the chromosome cannot be filled in.

(d) Older chromosomes are more fragile and the ends break off more frequently. (e) Telomerase is only functional in cancer cells. 7. Which type of enzyme makes a transient（短暂的）break in both DNA duplex strands and then transports another segment of a DNA molecule (or separate molecule entirely) through the break and reseals the severed strands? ___ _B _ a. topoisomerase I b. topoisomerase II c. topologicase I d. topologicase II e. isomerase I

Transcription:

1. Eukaryotic promoters are composed of ___ _A _ (a) The initiator box, the TATA box and upstream elements; (b) The -10 and the -35 regions; (c) Introns and exons;

2

(d) snRNPs and a complementary RNA; (e) A stem-loop structure.

2. In the following diagram of a eukaryotic gene, (B) would most likely represent___ _ C _

(a) Two exons that have been spliced together; (b) The enhancer; (c) The TATA box;

(d) The RBS (ribosome binding site); (e) The AUG start codon.

3. Which of the following is/are not found in Class II promoters（类型II启动子）？___ _D _ (a)UCE; (b)CCAAT box; (c) Box C; (d) a and c; (e) all of the above

4. Which of the following statements is true for the promoters of eukaryotic genes that use RNA polymerase II? ___ _B _ (a) The initiator box is downstream of both the AUG start codon and the TATA box;

(b) The TATA box is downstream of the upstream elements and upstream of the initiator box;

(c) The upstream elements are upstream of the promoter but downstream of the transcriptional start site;

(d) The TATA box is upstream of the transcriptional start site but downstream of the initiator box; (e) The initiator box is upstream of the first exon and downstream of the translational start site. 5. Addition（增加）of polyA to the 3' end of mRNA requires___ _E _ (a) polyA polymerase (PAP); (b) RNA cleavage;

(c) CPSF; (d)a and c; (e)all of the above 6. Nuclear mRNA splicing is performed（由…完成）___ _E _ (a)in nucleosomes; (b)in spliceosomes; (c)in the nucleolus; (d)by RNA only; (e)b and c

7. Which of the following statements regarding introns is FALSE? ___ _A _ (a) Absolutely no bacteria have genes with introns; (b) Introns are usually transcribed but not translated;

(c) Introns can be removed either through self-splicing or enzyme-mediated splicing; (d) In some circumstances, introns are retained in the mature mRNA;

(e) Introns are removed from the primary transcript while it is still in the nucleus. 8. Which of the following statements is true? ___ _D _ (a) Exons are translated but not transcribed; (b) Exons are replicated but introns are not; (c) Both exons and introns are translated; (d) Introns are transcribed but not translated; (e) Exons are transcribed but not translated.

9.The Cap and Tail of eukaryotic messenger RNA consist of the following___ _C _ (a) The Cap consists of the sequence AAAUAA added at the 5'-end;

(b) The Cap contains a single guanine nucleotide and the tail contains many methylated adenosine nucleotides; (c) The Cap contains a single methylated guanine nucleotide and the tail contains many adenosine nucleotides;

(d) The Tail consists of a long sequence of A's added at the 5'-end; (e) The Cap consists of a single guanine nucleotide added at the 3'-end.

3

10. The site on DNA to which RNA polymerases bind before initiating transcription（起始转录） is called the ___ _C _ a. terminator b. operator c. promoter d. enhancer e. silencer

11. In addition to binding RNA polymerases, what other functions do promoters seem to perform? ___ _E _ a. They specify which strand of DNA to transcribe. b. They specify which strand of DNA to translate. c. They specify the site at which translation begins. d. They specify the site at which transcription begins. e. a and d

12. Once the sigma factor leaves the core enzyme（核心酶）, what happens? ___ _A _ a. Transcription begins.

b. The core enzyme continues synthesis. c. The core enzyme discontinues synthesis. d. Transcription terminates. e. c and d

13.Heterogeneous nuclear RNAs （核内不均一RNA，hnRNA）are ___ _B _ a. tRNA precursors b. mRNA precursors c. rRNA precursors

d. snoRNA precursors e. b and c

14. Why must RNA splicing be absolutely precise（准确）? ___ _C _ a. A single base error at a splice junction will cause a large deletion. b. A single base error at a splice junction will cause a large addition.

c. A single base error at a splice junction will change the reading frame and result in mRNA mistranslation.

d. A single base error at a splice junction will cause a large inversion

15. What is sometimes needed for the termination（终止）of bacterial transcription? ___ _B _ a. a gamma protein b. a rho protein c. a row protein

d. a rho carbohydrate e. a nu factor

16. Messenger RNA longevity（寿命）is often related to what features of the molecule? __ _E _ a. the 5’-CAP

b. the length of the first intron c. the poly(A) tail d. both a and b e. both a and c

Translation:

1. During translation in E. coli, charged tRNAs bind and interact with___ _C _ (a) only the 50S subunit; (b) the P site; (c) the A site; (d) the E site; (e) all of the above.

4

2. What class of RNA is required during protein synthesis（合成）to help convert the language of nucleotides (DNA and RNA) to that of amino acids? ___ _C _ a. miRNAs b. rRNAs c. tRNAs d. mRNAs e. hnRNAs

3. If there were one tRNA for every codon that codes for an amino acid, how many different tRNAs should there be? ___ _D _ a. 20 b. 3 c. 64 d. 61 e. 2

4. At which site on the ribosome do the aminoacyl-tRNAs（氨酰tRNA）generally enter the ribosome? ___ A_

a. A site b. P site c. E site d. C site e. T site

5. What is the name of the enzyme that forms the peptide bond（肽键）and of what is the enzyme composed? ___ _C _ a. peptidase, RNA b. peptidase, protein

c. peptidyl transferase, RNA d. peptidyl transferase, protein e. peptidyl transferase, polypeptide

Mutations and repair:

1. Which of the following does NOT cause a frameshift（移码）? ___ _C _ (a) Insertion of one base into a coding region; (b) Deletion of five bases from a coding region; (c) Insertion of three bases into a coding region; (d) Deletion of two bases from a coding region; (e) Insertion of three bases into a regulatory region

2. A base analog（碱基类似物）is a chemical that___ _A _ (a) Converts one base to another by altering amino groups to hydroxy groups;

(b) Hydrolyses pyrimidine bases off from the deoxyribose to which they were attached; (c) Distorts a DNA double helix by binding to base pairs;

(d) Is mistakenly incorporated into DNA by DNA polymerase; (e) Absorbs ultraviolet radiation and reacts with DNA.

3. Base deamination（脱氨）can cause single base pair mutations because___ _D _ (a) deaminated G structurally resembles U; (b) deaminated G can base pair with U;

(c) deaminated C structurally resembles A.; (d) deaminated C can base pair with A.

4. The three enzymes that play a role during excision repair（切除修复）are, in order___ _E _ (a)nuclease, RNA polymerase, ligase; (b)nuclease, DNA polymerase I, excisionase; (c)spliceosome, nuclease, ligase; (d) RNA polymerase I, ligase, methylase; (e)nuclease, DNA polymerase I, ligase.

5. The mismatch repair system is able to distinguish（区分）the parent strand from the daughter strand (immediately following replication) because___ _A _ (a) the parent strand is methylated but the daughter strand is not;

5

(b) the daughter strand is phosphorylated but the parent strand is not; (c) DNA polymerase is still attached to the parent strand;

(d) the parent strand has a 5' cap but the daughter strand does not;

(e) the Okazaki fragments of the daughter strand have not yet been ligated together. 6. Any of the following will result in a silent mutation EXCEPT___ _D _ (a) a mutation that occurs in a non-coding region; (b) a mutation that occurs in a non-regulatory region;

(c) a mutation in which the third base of a codon is changed but the codon still codes for the same amino acid;

(d) a mutation that occurs in the splice junction of an intron;

(e) a mutation that occurs in an intron but not at the splice junction and branch site.

7. The creation of a stop codon in the middle of a coding sequence within the gene is called a ___ _C _ a. missense mutation b. frameshift mutation c. nonsense mutation d. point mutation e. silent mutation

Regulation of gene expression:

1. Which of the following is NOT a feature of eukaryotic gene expression? ___ _C _ (a) polycistronic mRNAs are very rare;

(b) many genes are interrupted by non-coding DNA sequences;

(c) RNA synthesis and protein synthesis are coupled as in prokaryotes; (d) mRNA is often extensively modified before translation;

(e) multiple copies of nuclear genes, and pseudo genes can occur. 2. An operon（操纵子）consists of___ _B _ (a) All the genes for one biosynthetic pathway;

(b) A cluster of genes which are transcribed into a single mRNA; (c) Several ribosomes attached to the same mRNA molecule;

(d) The two nearby sequences on DNA where RNA polymerase binds; (e) The group of codons which all code for the same amino acid. 3. In positive regulation（正调控）___ _D _

(a) an activator protein binds DNA at a site called the operator; (b) a gene is always transcribed;

(c) constitutively expressed genes are turned off;

(d) an activator protein helps RNA polymerase bind the promoter; (e) none of the above is true.

4. Regulation（调控）of β-galactosidase（β-半乳糖苷酶）synthesis（合成）is___ _D _ (a) under neither positive nor negative control; (b) under only positive control;

(c) under only negative control; (d) under both positive and negative control.

5. In the presence of glucose（葡萄糖）and the absence of lactose（乳糖）___ _C _ Both the LacI 阻遏物 and the Crp protein will bind to the DNA; Neither LacI nor Crp protein will bind to the DNA;

6

Crp protein will not bind to DNA but the LacI 阻遏物 will; Crp protein will bind to DNA but the LacI 阻遏物 will not.

6. Which of the following statements describes a step in the regulation of the lac operon___ A_ (a) A cyclic AMP-CAP complex binds to the CAP site;

(b) The 阻遏物 binds to CAP to form an inactive 阻遏物;

(c) Cyclic AMP competes with the 阻遏物 for binding to the operator;

(d) The 阻遏物 undergoes a conformational change upon binding cyclic AMP. 7. Antisense RNA（反义RNA）can regulate genes by binding to the___ _A _ (a) mRNA;

(b) Small subunit of the ribosome; (c) RNA polymerase; (d) 23s rRNA

(e) initiator tRNA.

8. Which of the following sites may be thousands of base pairs away from a promoter, yet regulate transcription? ___ _C _ (a)Operators; (b) initiators; (c) enhancers; (d) all of the above; (e) none of the above. 9. Regulatory sequences known as enhancers___ _C _ (a) are needed for transcription by RNA polymerase III but not by RNA polymerase II; (b) Encode the snRNA molecules needed for splicing RNA; (c) May be located upstream or downstream of the promoter;

(d) Are where RNA polymerase first binds when it transcribes a gene;

Transposons:

1. At the two ends of an insertion sequence（插入序列）you would expect to find___ _A _ (a) Inverted repeats;

(b) Single stranded overhangs generated by restriction enzymes; (c) GC rich regions whose melting temperature is higher; (d) Short segments of RNA;

(e) Short tandem repeats of about 6 base pairs

2. DNA sequences that on rare occasions（低频率）move from one place in the genome to another are called ___ _C _ a. movers b. jumpons c. transposons d. transpodons e. jumposons

Techniques in molecular biology:

1. Which statement is NOT true about nucleic acid hybridization（杂交）? ___ _B _ (a) it depends on complementary base pairing;

(b) a polysaccharide can hybridize with a DNA strand ; (c) a DNA strand can hybridize with another DNA strand; (d) an RNA strand can hybridize with a DNA strand;

7

本文来源：https://www.bwwdw.com/article/oxo.html