49. Active transcription occurs on
(A) centromere
(B) telomere
(C) cytosome
(D) heterochromatin
(E) euchromatin

45. DNA methylation (A) increases transcription. (B) inhibits transcription. (C)increases crossover events. (D) decreases crossover events. (E) promotes post-translational modification of proteins.

46. These are the only vertebrates in which blood flows directly from respiratory organs to body tissues without first returning to the heart. (A) Amphibians (B) Birds (C) Fishes (D) Mammals (E) Reptiles

47. The clonal selection theory is an explanation for (A) how a single type of stem cell can produce both red blood cells and white blood cells. (B) how antibody proteins can be molded to fit antigens after the antigen interacts with the antibody-producing type of cell. (C)how an antigen can induce the multiplication of B cells to result in production of high levels of specific antibodies. (D) how HIV can disrupt the immune system. (E) how macrophages can recognize specific T cells and B cells.

48. ________ is a water-soluble hormone derived from the nervous system that regulates blood volume and blood pressure? (A) Antidiuretic hormone (B) Aldosterone (C) Cortisol (D) Oxytocin (E) Adrenocorticotropic hormone

50. Which of the followings is an example of post-transcriptional gene processing? (A) DNA methylation (B) histone acetylation (C) RNA splicing (D) proteasome regulation (E) chromatin modification

1. Which of the following names is correct? (A) iodine trichlorite, ICl3 (B) phosphorus pentoxide, P2O5 (C) chlorous acid, HClO2 (D) lithium hydrogen, LiH (E) calcium(II) oxide, CaO

2. Calculate the pH of a 0.010 M aluminium chloride solution. The Ka value for Al(H2O)63+ is 1.4 × 10-5. (A) pH=1.35 (B) pH=2.38 (C) pH=3.43 (D) pH=4.31 (E) pH=5.36

3. Hydrogen cyanide gas (HCN), a powerful respiratory inhibitor, is highly toxic. It is a very weak acid (Ka =6.2 ×10-10) when dissolved in water. If a 50.0 mL sample of 0.100M HCN is titrated with 0.100 M NaOH, calculate the pH of the solution at the equivalence point of the titration. (A) pH=3.05 (B) pH=8.49 (C) pH=9.21 (D) pH=10.95 (E) pH=11.36

4. Which of the following molecules are nonlinear?NO2–, C2H2, N3–, HCN, CO2, H2O2 , N2O (central atom is N) (A) C2H2, HCN (B)NO2–, H2O2 (C)CO2, N3–(D) N3–, NO2–(E) N2O, H2O2

5. Calculate the concentration of Ag+ in a solution prepared by mixing 150.0 mL 1.0×10－3 M AgNO3 with 200.0 mL 5.00 M Na2S2O3.(K1 = 7.4×108, K2 = 3.9×104) (A) 1.8 x 10-18 mol/L (B) 4.3 x 10-4 mol/L (C) 3.8 x 10-9 mol/L (D) 8.30 x 10-4 mol/L (E) 2.86 x 10-3 mol/L