40. Proteins that bind to DNA and turn on operons by making it easier for RNA polymerase to bind to a promoter are called
(A) promoters.
(B) operators.
(C) activators.
(D) inducers.
(E) enhances.

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

41. A typical eukaryotic cell may contain tens of thousands of genes, but only a small fraction of them are expressed at the same time. In this case, (A) the default state of most genes is usually set to be on. (B) the default state of most genes is usually set to be off. (C) most un-expressed genes are deleted from the genome. (D) most expressed genes are copied several times. (E) most expressed genes are joined together.

42. Splice sites in pre-mRNA are marked by two universally conserved sequences contained (A) in the middle of the intron. (B) in the middle of the exon. (C) at the ends of the exons. (D) at the ends of the introns. (E) one in the intron and the other in the exon.

43. Which type of RNA participates in nuclear export of mRNA? (A) snRNA (B) miRNA (C) snoRNA (D) tRNA (E) hnRNA

44. Synthesis of pre-rRNA occurs in the (A) cytoplasm. (B) endoplasmic reticulum. (C) extranucleolar area of the nucleus. (D) nucleus. (E) nucleolus.

45. If the third base of a codon is U, which of the following bases on the first position of an anticodon is usually NOT allowed? (A) A (B) G (C) I (D) U (E) any bases are allowed.

46. Active mTOR stimulates the overall rate of protein synthesis in the cell. Which of the following can activate mTOR? (A) presence of stress (B) presence of growth factors (C) low nutrients (D) low energy (E) none of the above