複選題

33. Which of the following statements regarding microRNAs is correct?
(A) They are commonly found in all living cells.
(B) Base-pairing to the target mRNA is not perfect.
(C) Expression of~5% of human genes is controlled by microRNAs.
(D) Most of them contain a poly( A ) tail.
(E) One microRNA recognizes only one mRNA, but one mRNA can be bound by more than one microRNA.

29. Which of the following statements regarding RNA splicing is correct? (A) It is an important mechanism for translational regulation. (B) It usually occurs in both prokaryotes and eukaryotes. (C) It requires GTP, instead of ATP, as the energy source. (D) It may produce different mRNA sequences from the same gene. (E) None of the above.

30. Which of the following statements on ribosome is correct? (A) Its molecular weight is about 100 KDa. (B) The RNA component contributes more to the mass than does the protein component. (C) The catalytic core is consisted of proteins. (D) It hydrolyzes ATP during reaction. (E) None of the above

31. Which of following events does not occur within the nucleus? (A) protein phosphorylation (B) RNA capping (C) polyadenylation (D) splicing (E) ribosomal RNA synthesis

32. Which of the following techniques is generally used to detect DNA-protein interactions? (A) SDS-PAGE (B) in situ hybridization (C) electrophoretic mobility shift assay (D) Southern blotting (E) yeast two-hybrid system

34. Self-splicing introns (A) use ATP as the energy source. (B) are found mainly in pre-mRNA. (C) function through a single trans-esterification reaction. (D) are a type of ribozymes. (E) use calcium ions as a cofactor.

複選題35. Which of the following statements regarding ribosome reading frames is correct? (A) There are two possible reading frames for a given mRNA sequence. (B) A reading frame defines an amino acid sequence. (C) The ribosome may read mRNA in the 5' to 3' or in the 3' to 5' direction. (D) The ribosome will always follow the same reading frame during translation. (E) The ribosome may follow a reading frame composed of di- or tri-nucleotides.

36. How does the interaction between the lac repressor and the lac operator block transcription initiation? (A) lac repressor binding blocks RNA polymerase from interacting with DNA at the start site. (B) lac operator induces a conformational change in lac repressor. (C) lac repressor binding causes a conformational change in RNA polymerase. (D) lac operator blocks DNA polymerase from interacting with the transcription start site. (E) lac repressor binding induces a protease that degrades the sigma subunit of RNA polymerase.

37. Which of the following statements about the essential carboxyl terminal domain (CTD) of RNA polymerase is NOT true? (A) The CTD can bind different factors. (B) The CTD can become phosphorylated. (C) The CTD is present in RNA polymerase I, II, and III. (D) The CTD is critical for viability. (E) The CTD may contain many repeats of a heptapeptide.

38. Which of the following is not a structural motif found in a DNA-binding domain? (A) stem-loop (B) zinc-finger (C) helix-loop-helix (D) leucine-zipper (E) homeodomain

39. Where do transcription and translation occur in prokaryotic cells? (A) on the plasma membrane (B) in the nucleus (C) in the cytoplasm (D) in the nucleus and then in the cytoplasm (E) in the cytoplasm and then in the nucleus