27. Which of the following statements regarding immune response is correct?

(1) In cellular immunity, T lymphocytes, including cytotoxic T lymphocytes and killer T cells are responsible for the recognition and killing of foreign invaders. 

(2) Killer T lymphocytes have an especially low count in a patient with advanced AIDS.

(3) Histamine is produced by host cells infected by viruses. 

(4) Immunological memory is due to long lived B cells that secrete a specific antibody.
(A) (1) and (2) are correct
(B) (1) and (3) are correct
(C) (1) and (4) are correct
(D) (1), (2) and (4) are correct
(E) (1), (3) and (4) are correct

23. Which of the following statements regarding extracellular vesicles (EVs) is incorrect? (A) Exosomes and microvesicles both are extracellular vesicles (EVs) but differ in their cellular origin. The exosomes bud off from the cell membrane but MVs have endocytic origin. (B) EVs contain mRNAs and miRNAs and those EV-associated mRNAs and miRNAs can be functionally transferred to recipient cells. (C) Tumor cells have been shown to exploit EVs to contribute to their progression by inactivating T lymphocytes or natural killer cells as well as promoting differentiation of regulatory T lymphocytes to suppress immune reactions. (D)Several pathogenic proteins such as prions and β-amyloid peptides have also been reported to exploit exosomes in order to propagate to other cells. (E) None is incorrect

24. Which of the following statements regarding stem cells is correct? (1) Pluripotent stem cells have the potential to become an entire organism. (2) Totipotent stem cells can form any of the three embryonic germ layers, but cannot give rise to an entire organism. (3) Multipotent cells can develop into more than one cell type, but are more limited than pluripotent cells. (4) Totipotent, pluripotent or multipotent stem cells are cells that have the capacity to self-renew by dividing asymmetrically. (A) (1) and (2) (B) (2) and (3) (C) (3) and (4) (D) (1) and (4) (E) (2) and (4)

25. Activation of the notch receptor by its ligand, delta, in neighboring cell populations defines patterns of distinct differentiated cell types among cells that have the potential to adopt the same fate. What is this process called? (A) Lateral inhibition (B) Neurulation (C) Invagination (D) Gastrulation (E) None of above

26. Which of the following statements regarding heterotrimeric G protein and G-protein-mediated signaling is correct? (1) The alpha subunit of heterotrimeric G protein (G-alpha), belong to the larger group of enzymes called GTPase. (2) There are several different classes of heterotrimeric G-proteins that are defined by their different G-alpha, G-beta or G-gamma subunits. (3) G-protein coupled receptors (GPCRs) associate with heterotrimeric G-proteins. Upon ligand binding to GPCRs, G-alpha hydrolyze bounded GTP to GDP and dissociate from the other subunits of heterotrimeric G-proteins. (A) (1) and (2) (B) (1) and (3) (C) (2) and (3) (D) All are correct (E) None is correct

28. The order for the construction of a cDNA fragment from mRNA is to: (A) treat with reverse transcriptase, digest with RNase, add G residues to the 3' end, bind oligo-dC, treat with DNA polymerase and bind oligo-dT. (B) digest with RNase, add G residues to the 3' end, treat with reverse transcriptase, add G residues to the 3' end and treat with DNA polymerase. (C) bind oligo-dT, treat with reverse transcriptase, digest with RNase, add G residues to the 3' end, bind oligo-dC, treat with DNA polymerase. (D) bind oligo-dC, treat with reverse transcriptase, digest with RNase, add G residues to the 3' end, bind oligo-dT and treat with DNA polymerase. (E) None of above is correct

29. Which one is NOT involved in COPII vesicle formation? (A) GTPase Sar1 (GTP-bound state) (B) guanine nucleotide exchange factor (GEF) Sec12 (C) Coat Sec23/Sec24 heterodimer. (D) Outer coat Sec13/Sec31 heterotetramer (E) From Golgi to lysosome

30. Which molecule is degraded by ubiquitination during sister chromatid separation? (A) Cohesin (B) Securin (C) Cyclin A (D) Cdk2 (E) Cdk1

31. Which one CANNOT be used as a molecular "brake" for the immune system? (A) PD1 (B) PD-L1 (C) EGFR (D) NKG2A (E) CTLA4

32. Which one is NOT correlated with longevity? (A) high levels of plasma sphingomyelin (B) low levels of PUFA-containing triacylglycerols (C) high level of plasma cholesterol (D) tryptophan (E) high energy expenditure

33. Which one has asymmetric cell division? (A) Hepatocyte (B) Splenocyte (C) Intestinal epidermal cell (D) Stem cell (E) Skin cell