47. The main function of the atrioventricular (A-V) node is to
(A) initiate the heartbeat.
(B) set the rhythm of the heartbeat.
(C) relay the signal for the heart to contract from the left ventricle to the left atrium.
(D) relay a signal for the ventricles to contract.
(E) detect the vibration of heart.

43. Mammals are homeostatic for all of the following EXCEPT (A) Body temperature (B) Blood glucose concentration (C) Blood pH (D) Metabolic rate (E) Blood calcium concentration

44. Which of the following is true for the phenomenon of "epistasis" in genetics?(A) It is a type of gene interaction in which the phenotype expression of one gene alters that of another independently inherited gene.(B) It is the inheritance of traits transmitted by mechanisms that do not involve the nucleotide(C) It only occurs in mammals.(D) It is the mechanism for the inheritance of organelles.(E) It controls the early development of Drosophila.

45. The nontemplate strand of a portion of a gene reads: 5' -TTCACTGGTTCA. What is the sequence of the resulting transcript (RNA) for this portion? (A) 5'-AAGUGACCAAGU (B)5'-UGAACCAGUGAA (C)5'-UUCACUGGUUCA (D) 5'-ACUUGGUCACUU (E) 5'-TGAACCAGTGAA

46. During protein synthesis, which of the following proteins interacts via its N-terminal sequence with the signal recognition particle (SRP)? (A) Nuclear matrix protein (B) Lysosomal protein (C) Ribosomal protein (D) Mitochondrial protein (E) Chloroplast protein sequence.

48. Which of the following statements about fungi is true? I. They are eukaryotic. Ⅱ. They all have rigid cell walls.III. Most are filamentous.IV. Some are photosynthetic.V. They are capable of only asexual reproduction. (A) I. II. V (B) I. II. III (C) I. II.IV (D) I. II. IV. V (E) I. II. II. IV

49. Which of the following is present in double-stranded cDNA but absent in the corresponding genomic DNA of eukaryotic cells? (A) Promoter sequences (B) A homopolymeric sequence of A:T base pairs (C) Intron sequences (D) 5' and 3'UTRs (E) Exon sequences

50.Which of the followings are the RNA-protein complex: I. Ribosome Il. Nucleosome III. Lysosome IV. Spliceosome V. Telomerase(A) I, II, IV(B) I, II, III, IV(C) I, III, IV, V(D) I, IV, V(E) I, II, II, IV, V  

51. Which of the following is incorrect for the function of glia in the CNS of adult vertebrates? (A) Ependymal cells help form the blood-brain barrier. (B) Astrocytes can act as stem cells. (C) Oligodendrocytes myelinate axons in the CNS. (D) Microglia are immune cells in the CNS. (E) Astrocytes promote blood flow to neurons.

52. Which plant hormone is incorrectly paired with its function? IV. Spliceosome V. Telomerase (A) Auxin - promotes stem growth through cell elongation (B) Cytokinins - initiate programmed cell death (C) Gibberellins - stimulate seed germination (D) Abscisic acid - promotes seed dormancy (E) Ethylene - inhibits cell elongation

53. Which of the following vitamins is correctly associated with its use? (A) Vitamin C - curing rickets (B) Vitamin A - incorporated into the visual pigment of the eye (C) Vitamin D - calcium removal from bone (D) Vitamin E - protection of skin from cancer (E) Vitamin K - production of white blood cells