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.

10. Which of the following is not needed for mammalian cell polyadenylation of pre-mRNA? (A) RNA polymerase (B) RNA polymerase II (C) PAP (D) CPSF (E) PABII

11. In human global genome nucleotide excision repair (GG-NER), which products are correct for the "incision" function? (A) XPF and XPG (B) XPB and XPD (C) ХРА and XPC (D) XPA and XPB

複選題12. Choose a right statement on Telomerase or Telomere (A) Telomerase was first observed in Tetrahymena micronuclei extracts. (B) Telomerase is a unique enzyme in that it is composed of only RNA. (C) Without telomeres, linear eukaryotic chromosomes would get shorter and shorter with each round of DNA replication (D) All organisms must protect their telomeres from nucleases and double strand break repair enzymes.

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.

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.

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

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.