17. Which of the following factors is involved in proofreading during transcription?
(A) NusA
(C) sigma-factor
(E) GreB
(B) RecA
(D) rho-factor

13. Select one of the choices below to indicate whether it is a characteristic of miRNA or siRNA. (A) miRNAs function to silence gene expression primarily by blocking transcription of targeted mRNAs. (B) siRNA induces degradation of the target mRNA. (C) miRNAs usually base-pair perfectly with target mRNA (D) siRNAs are formed by cleavage from a stem-loop RNA.

複選題14. Which following statement is right during homologous recombination? (A) RecBCD has a DNA exonuclease activity (B) RecA and RecB are involved in branch migration of a Holliday junction (C) RuvC could bind to and resolve Holliday junctions (D) Spo11 creates single strand breaks in DNA in baker yeast.

15. Which of the following statements is true about a lac operon with this genotype? (a mutant repressor gene whose product cannot bind to the lac operator) (A) The operon is repressible. (B) The operon is nonrepressible. (C) The mutation is recessive. (D) The mutation is trans-dominant. (E) None of the choices is correct.

16. Which of the following statement is correct regarding the sigma-factor? (A) Subregions 2.4 and 4.2 are involved in operator recognition. (B) It determines rifampicin sensitivity or resistance. (C) Interaction with the core enzyme unmasks the DNA-binding region. (D) The 2.4 region has a B-sheet domain. (E) It can bind to the up element.

18. Which of the following is the best way to determine the base content of DNA? (A) gel electrophoresis (B) spectrophotometry (C) x-ray diffraction (D) density gradient centrifugation (E) deoxyribonuclease treatment

19. In which of the following situations is a silent mutation least likely? (A) change in a sequence in the 5' UTR. (B) change in a sequence in the 3' UTR. (C) change in a sequence in an exon. (D) change in the sequence in the promoter. (E) change in a sequence in an intron.

20. During an experiment to study the rate of infection of bacteria with λ phage, the bacterial cultures were accidentally exposed to a UV light source. Which of the following would be expected for this exposure? (A) Coprotease activity in RecA protein is activated. (B) recA gene is turned off. (C) Coprotease activity in repressor is activated. (D) Lysogenic cycle is induced. (E) SOS response is turned off.

複選題21. Which of the following statement is       true      ? (A) Eukaryotic RNA polymerase III makes tRNAs and snRNAs (B) Rpbl of yeast RNA polymerase is homologous to alpha-subunit of bacterial RNA polymerase (C) Rpb5 of yeast RNA polymerase II is also a component of RNA polymerase I and III (D) Zipper is a protein loop within eukaryotic RNA polymerase II and is involved in initiating dissociation of the RNA-DNA hybrid (E) Yeast RNA polymerase contains 10 apparent subunits and four of them are phosphorylated

22.Which of the following statement is       not true       for eukaryotic gene promoters? (A) For the promoters recognized by RNA polymerase II (class II promoters), TATA-less promoters are commonly found in housekeeping and developmentally regulated genes (B) Initator is required for optimal transcription of some class II promoters; one classic example is the adenovirus major late promoter (C) Class I promoters (the promoters recognized by RNA polymerase I) are quite variable in sequence across species, while they all contain a conserved AT-rich initator (rINR) (D) Some of the class I promoters are located entirely within the genes themselves, one example is the 5S rRNA gene (E) Some of class III promoters (the promoters recognized by RNA polymerase III) resemble those found in class II genes, one example is the 7SL gene

23. Please predict the possible consequence of blocking the       action of TFIIF      , a general transcription factor of RNA polymerase II. (A) The TFIIDAB complex will not form (B) Polymerase may not bind to the DAB complex (C) TFIIA will not bind to TFIID (D) The TFIIDAB complex will not form and TFIIA will not bind to TFIID (E) Transcription elongation is enhanced by limiting nucleotide misincorporation