28. An enhancer
(A) is a protein that binds to RNA polymerase and stimulates transcription.
(B) is a metabolite that stimulates transcription of eukaryotic promoters.
(C) interacts with repressor proteins to enhance transcriptional activity.
(D) acts as a binding site for RNA polymerase.
(E) none of the above.

24. Which of the following sequential order for the secretory pathway is false? (A) Rough endoplasmic reticulum (ER) → ER-to-Golgi transport vesicles → Golgi cisternae → secretory vesicles. (B) Rough ER → ER-to-Golgi transport vesicles → Golgi cisternae → Mitochondria. (C) Plasma membrane → Early endosome → Late endosome → Lysosome. (D) Rough ER → ER-to-Golgi transport vesicles → Golgi cisternae → Late endosome → Lysosome.

25. The first step in the secretory pathway that should be inhibited by a dominant-negative mutant of SNARE proteins is (A) rough endoplasmic reticulum to Golgi transport. (B) intra Golgi transport. (C) trans Golgi network (TGN) transport to the plasma membrane. (D) TGN transport to the late endosome.

26. Which of the following statements about tRNA is correct? (A) There are 61 different types of tRNAs. (B) Stop codons are recognized by specialized tRNAs. (C) Aminoacyl-tRNA is formed by joining the amino group of an amino acid to a tRNA. (D) The amino acid residue, instead of the anticodon, determines the specificity of an aminoacyl-tRNA. (E) Each tRNA folds into a unique structure for codon recognition.

27. What is a Shine-Dalgarno sequence? (A) It is a pyrimidine-rich stretch. (B) It is complementary to the 3'-end of the 23S ribosomal RNA. (C) It is usually followed by a stop codon. (D) It usually forms a stem-loop structure. (E) It is located at the 5' UTR.

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

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.

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.