19. The first step of tRNA charging catalyzed by the aminoacyl-tRNA synthetase is:
(A) Reaction of the amino acid with ATP.
(B) Reaction of the amino acid with GTP.
(C) Transfer of the amino acid to the 3' end of tRNA.
(D) Transfer of the amino acid to the 5' end of tRNA.
(E) Binding of the amino acid to the anticodon loop.

16. A special form of RNA editing found in the mitochondria of trypanosomes and mediated by guide RNAs is deletion and insertion of: (A) adenine. (B) uracil. (C) guanine. (D) cytosine. (E) inosine.

17. The Drosophila Dscam gene contains 48 alternative forms of exon 6. What is the mechanism for having only one exon 6 variant in the mature mRNA? (A) Splicing factors cannot bind to more than one splicing site due to steric hindrance. (B) Spliced mRNA with more than one exon 6 variant leads to nonsense-mediated RNA decay. (C) The docking site binds to only one selector sequence located upstream of the exon6 variant. (D) Each exon 6 variant contains different sequences at the splicing sites. (E) Only the exon 6 variant that recruits enough SR proteins is retained in the mature RNA.

18. What is the function of the Shine-Dalgarno sequence? (A) It recruits the RNA polymerase. (B) It recruits the core transcription factors. (C) It recruits the initiation factors (D) It recruits the large ribosomal subunit. (E) It recruits the small ribosomal subunit.

20. Which of the following statements is correct regarding upstream open reading frames (uORFs)? (A) uORFs can be found in both eukaryotes and prokaryotes. (B) uORFs can be found in both 5' and 3' untranslated regions. (C) The presence of uORFs typically causes an increase in protein expression. (D) Translation of the open reading frame (ORF) encoding the yeast activator Gcn4 is inhibited when amino acids are deficient, because the ribosome moves slowly along the uORFs and then dissociates. (E) The size of uORFs is typically more than 20 codons.

21. Which of the following bacterial elongation factors (EFs) catalyzes translocation of the tRNA and mRNA and causes conformational changes of the ribosome? (A) EF-Tu. (B) EF-Ts. (C) EF-G. (D) EF-P. (E) EF-4.

複選題22. Which of the following statements is correct regarding the wobble base pair? (A) The wobble base pair follows Watson-Crick base pair rules. (B) The wobble base pair takes place at 3' end of the tRNA anticodon. (C) Hypoxanthine (I) can pair with uracil (U), adenine ( A ), or cytosine ( C ). (D) Guanine (G) can pair with adenine ( A  ) or cytosine ( C ). (E) The Wobble hypothesis predicts that the minimum requirement to satisfy all possible codons is 21 tRNAs.

23 Which of the following statements is correct regarding translation termination in eukaryotes? (A) The structure and amino acid sequence of the Class I eukaryotic release factors (eRFs) are similar with those of the Class I release factors in prokaryotes. (B) eRF1 induces release of the nascent polypeptide from the peptidy1-transferase center. (C) Rlil is an ATP-binding protein and brings eRF 1 to the ribosome. (D) eRF3 is a GTP-binding protein and catalyzes release of eRF1 from the A-site. (E) Neither eRF1 nor eRF3 participates in separation of the large and small ribosomal subunits after release of the nascent polypeptide.

24. Both the catabolite activator protein (CAP) and the Lac repressor can bind DNA, but why does CAP facilitate transcription while the Lac repressor represses transcription? (A) CAP and the Lac repressor use different structural motifs to bind DNA. (B) CAP binds to the region overlapping the promoter, while the Lac repressor binds to the region at a distance from the promoter. (C) The Lac repressor can interact with the RNA polymerase to inhibit transcription. (D) CAP has an activating surface that recruits the RNA polymerase. (E) CAP binds as a homodimer, while the Lac repressor binds as a homotetramer.

25. Which of the following is the key bacteriophage X regulatory protein that acts as an activator and establishes lysogeny upon infection of a new host? (A) CI. (B) CI. (C) CIII. (D) Cro. (E) Q

26. Which of the following DNA binding domains or motifs is found in most bacterial regulatory proteins? (A) Zinc-finger domain. (B) Basic leucine zipper motif. (C) AT-hook motif. (D) Helix-turn-helix motif. (E) Helix-loop-helix motif.