複選題
24. Regarding the mechanism of nuclear transport, which description is correct?
(A) NLS are protein sequences rich in positively-charged amino acids such as lysine and arginine that regulate protein cargos out of the nucleus.
(B) NES are oligonucleotides that direct protein cargos out of the nucleus.
(C) Molecules with a size of more than 5,000 Daltons can enter freely into the nucleus through nuclear pore complexes.
(D) The energy to transport macromolecules in or out of the nucleus is provided by the RAN ATPase cycle.
(E) Macromolecules require karyopherins to enter or leave the nucleus.

20. An RNA-dependent DNA polymerase that carries the RNA template with it to synthesize repeats at the 3'-ends of chromosomes is called: (A) DNA ligase (B) telomerase (C) DNA polymerase y (D) topoisomerase (E) DNA polymerase B

21. The steroid hormone glucocorticoid can enter cells and bind with glucocorticoid receptor (GR) to regulate gene expression. Which is incotrect? (A) GR is in the cytoplasm in the absence of glucocorticoid. (B) GR is a leucine-zipper-containing transcription factor. (C) Glucocorticoid-bound GR can form a homodimer to bind to GREs. (D) GR serves as a transcription activator or inhibitor depending on the gene context. (E) GR inhibits the expression of cytokine genes by tethering other transcription factors such as AP1 and NF-kB.

22. A diverse set of proteins with conserved RNA-binding domains associate with pre-mRNAs to assist RNA processing. Which is incorrect? (A) RRM (or RBD), KH motif and RGG box are conserved RNA-binding motifs. (B) Pre-mRNAs are associated with hnRNP proteins, contributing to splicing, polyadenylation and expott. (C) To identify hnRNP proteins, first high-dose UV irradiation causes covalent cross-links to form between RNA bases and associated protein, and are recovered by oligo-dT chromatography. (D) The specific monoclonal antibodies of idcntified hnRNP proteins are used to immunoprecipitate the hnRNP proteins complex. (E) All hnRNP proteins shuttle between the nucleus and the cytoplasm for RNA processing.

23. There are known mechanisms for translational control associated with mRNA-specific regulation； which statement is incorrect? (A) The iron-responsive element of the mRNA.provides steric hindrance to prevent the recruitment of the pre-initiation complex. (B) Maskin and Bicoid are the two mRNA-specific eIF4G-binding proteins that prevent the interaction with eIF4E. (C) The cytoplasmic-polyadenylation-element-binding protein binds to the 3' UTR of the mRNA through associations with Maskin. (D) Bicoid binds directly to the Biocoid response element Located at the 3' UTR of the mRNA. (E) Sex-lethal binds to the uridine-rich sequences located at the 3' and 5' UTRs of mRNA that inhibits translation.

25. Which of the following statement(s) is correct regarding to intracellular protein trafficking?(1) Vesicular transport is tightly regulated by small GTPase that cycles between GDP-bound and GTP-bound state.(2) COPII vesicles transport proteins from ER to Golgi while COPI vesicles transport proteins from Golgi to the plasma membrane.(3) Membrane fusion step is driven by GTP hydrolysis for the dissociation of SNARE protein complexes. (A) 1 only (B) 1 and 2 (C) 1 and 3 (D) 2 and 3 (E) All of above are correct.

26. Which of the following statement(s) is corect regarding to protein endocytosis or exocytosis?(1) Clathrin forms the triskelion structure for the polymerization of a polygonal lattice.(2) The acidic pH of endosomes causes receptor-ligand complexes to dissociate. The best example to describe the phenomenon is the endocytosis of transferrin receptor.(3) Transmission of nerve impulses at chemical synapses depends on the exocytosis of neurotransmitter-filled synaptic vesicles. (A) I and 2 (B) 2 and 3 (C) 1 and 3 (D) 3 only (E) All of above are correct.

27. Which of the following statements regarding G protein or G protein-mediated signal transduction is incotrect?(1) Epinephrine binding to the beta-adrenergic receptor causes an activation of adenylyI cyclase through the activation of a stimulatory G protein.(2) Gi alpha submit of the trimeric G proteins can inhibit adenylyl cyclase(3) Gq alpha submit of the trimeric G proteins can stimulate Pl-phospholipase C (A) I and 2 (B) I and 3 (C) 2 and 3 (D) all of the above. (E) none of the above.

28. Which of the following statement about membrane potential and action potential propagation is correct?(1) The resting potential of a typical neuron is -30 my.(2) The resting membrane potential of animal neurons depend largely on nongated K+ channels.(3) During an action potential, opening of voltage-gated Cazt channels happens first.(4) Repolarization during the refractory period is largely due to opening of voltage-gated K+ channels. (A) I and 3 (B) 2 and 4 (C) 1,2 and 4 (D) 1, 3 and 4 (E) 2. 3 and 4

29. Which of the following statements regarding stem cells is incotrect? (1) Endoderm and ectodern cells are pluripotent stem cells.(2) Cord blood stem cells are multipotent stem cells.(3) Lymphoid progenitors are oligopotent stem cells. (A) 1 only (B) 2 only (C) 3 only (D) 1 and 3 (E) 2 and 3

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