33. Which repair mechanism is primarily responsible for fixing thymine dimers caused by UV radiation?
(A) Base excision repair
(B) Mismatch repair
(C) Nucleotide excision repair
(D) Homologous recombination
(E) Non-homologous end joining

29. Which of the following statement about membrane potential and action potential propagation is NOT correct? (A) The resting membrane potential of animal neurons depend largely on non-gated K+ channels. (B) The resting potential of a typical neuron is -30 mV. (C) During an action potential, opening of voltage-gated Na+ channels happens first (D) Repolarization during the refractory period is largely due to opening of voltage-gated K+ channels. (E) All above are incorrect.

30. Which strategy is the current immune checkpoint blockade for cancer immunotherapy? (A) Anti-CTLA4 antibody (B) CAR-T therapy (C) Cancer vaccine (D) Bi-specific antibody (E) Antibody-dependent cytotoxicity

31. Re-replication during S phase results in DNA damage and genomic instability. Which one does NOT prevent the origin re-replication during DNA replication? (A) ORC, CDC6, CDT1, and MCM are the origin licensing factors. (B) Geminin directly binds to CDT1 to inhibit its licensing activity. (C) Dephosphorylation of pre-RC complex, MCM, ORC1, CDC6, and CDT1, represses reactivation of origins. (D) Cullin-based E3 ligases mediate the degradation of ORC1 and CDT1. (E) APC/C targets the degradation of CDC6 and CDT1

複選題32. Which one is responsible for DNA damage checkpoint? (A) APC/C E3 complex (B) Cul3-KLHL20 E3 ligase (C) Motor proteins (D) ATM kinase (E) ATR kinase

34. Which organelle plays a central role in initiating the intrinsic pathway of apoptosis? (A) Mitochondria (B) Endoplasmic reticulum (C) Golgi apparatus (D) Lysosomes (E) Peroxisomes

35. To study the function of the essential cyclin genes in yeast, researchers constructed a shuttlc vector in which a copy of the cyclin gene was ligated to the GAL1 promoter. The vector was then introduced into haploid yeast cells in which all copies of the cyclin genes had been disrupted. Following introduction of the vector, you would expect that (A) the yeast cells would grow on both glucose and galactose media. (B) the yeast cells would grow on glucose but not galactose medium. (C) the yeast cells would grow on galactose but not glucose medium. (D) on transfer to either glucose or galactose medium, the vector-carrying cells would eventually stop growing because of insufficient cyclinexpression. (E) none of the above

36. In intestinal epithelial cells, the different plasma membrane domains are separated from each other by special barriers. Which of the following statements is false? (1) These barriers are set up by nanoscale lipid raft domains.(2) Proteins normally cannot pass through these barriers, whereas any membrane lipid can do so freely. (3)The  asymmetric distribution of membrane proteins resulting from these barriers is functiona(4) These barriers are a result of proteins of the apical surface forming a large aggregate that excludes proteins of the other domains. (A) (I), (2) and (3) (B) (2), (3) and (4) (C) (1) and (4) (D) (1), (2) and (4) (E) All of the above

37.Whis of the following lipids do you expect to be a canonical scramblase substrate in the plasn (A) Galactocerebroside (B) Phosphatidylethanolamine (C) Glycosylphosphatidylinositol (D) Cholesterol (E) Ganglioside GMI

38."Housekeeping genes" in bacteria are commonly expressed constitutively, but not all of these genes are expr (the same number of molecules per cell). The primary mechanism responsible for variations in the lev enzymes from different genes is that: (A) all constitutive enzymnes are synthesized at the same rate, but are not degraded equally. (B) their promoters have different affinities for RNA polymerase holoenzyme. (C) some constitutively expressed genes are more inducible than others. (D) some constitutively expressed genes are more repressible than others. (E) the same number of mRNA copies are made from each gene but are translated at different rates.

39.The tryptophan operon of E.coli is repressed by tryptophan added to the growth medium. The tryptophan repr (A) binds to RNA polymerase when tryptophan is present. (B) binds to the trp operator in the absence of tryptophan. (C) binds to the trp operator in the presence of tryptophan. (D) is a DNA sequence. (E) is an attenuator.