34. In the large-scale production of a particular human protein in insect cells, the cDNA corresponding to the protein was modified so that the expressed protein would have six histidine residues at the C-terminus. The purpose of this modification was to
(A) facilitate transfer of the cDNA into the insect cells.
(B) provide a promoter for the transcription of the cDNA in insect cells.
(C) facilitate purification of the expressed protein though binding to an affinity column containing chelated nickel atoms.
(D) prevent degradation of the expressed protein by insect cell proteases.
(E) provide the protein solubility

30. Which method is NOT for detecting dead cells? (A) Trypan blue (B) Annexin V (C) Ki67 (D) Comet assay (E) Cleaved caspase-3

31. Which method can determine cells at the S phase? (A) PARP1 immunoblotting (B) Cyclin D immunoblotting (C) CFSE staining (D) BrdU incorporation (E) Cohesion cleavage

32. What kind of treatment does anti-PD1 or anti-PDL1 antibody work for cancer immunotherapy? (A) mRNA vaccine (B) Immune checkpoint blockade (C) CAR-T cell therapy (D) Precision medicine (E) autoimmunity

33. Which of the following repair pathway is mainly a response for repairing DNA double-stranded breaks? (A) base excision repair (B) nucleotide excision repair (C) mismatch repair (D) homologous recombination repair (E) proofreading polymerases

35. What method can be used to functionally inactivate a gene without altering its sequence? (A) gene knockout (B) RNA interference (C) dominant negative mutation (D) CRISPR-Cas9 genome editing (E) only B and C

36. Which of the following changes is more likely to further confine a membrane protein within a corral established by the cortical cytoskeletal network? (A) Binding to an extracellular ligand (B) Binding of the protein to other transmembrane proteins (C) Increased temperature (D) Protease cleavage of the cytosolic domain of the protein (E) Protease cleavage of the extracellular domain of the protein

37. Which of the following is correct regarding both Cas9 and EcoRI?(1) They are both endonucleases.(2) They both create double-strand breaks in DNA.(3) They both recognize their target sequences with the help of guide RNAs.(4) They are both part of bacterial defense mechanisms against foreign DNA.(5) They are both greatly useful in manipulating DNA and studying gene expression. (A) 1 only (B) 1,2 and 5 (C) 2,3 and 5 (D) 1, 2, 4 and 5 (E) All

38. All are true for transcription activation except: (A) takes place when a transcriptional activator protein bound to DNA makes protein : protein contacts with RNA polymerase. (B) the degree of transcriptional activation is proportional to the strength of the protein : protein interaction. (C) a nucleotide sequence binding site for a DNA-binding protein serves as an activator site if DNA-binding protein can interact with promoter-bound RNA polymerase. (D) if the DNA-bound transcriptional activator makes contact with two different components of RNA polymerase, the transcription is markedly elevated. (E) All are true.

39. Which one of the following does not contribute to the activation of transcription in eurkaryotes? (A) SWISNF chromatin remodeling proteins (B) Histone acetyltransferases (C) Histone methylases (D) Histone deacetylases (E) Alterations in histone content

40. Enzymes that acetylate the s-amino group of lysine in the histidine tails are called_____and are involved in________. (A) histone deacetylases； restoring chromatin to a repressed state (B) histone acety1transferases (HATs)； initial events in transcriptional activation (C) histone activases； formation of the de-repression complex (D) Schiff base formation； promoting the formation of closed complexes (E) None of the above