88. Selenocysteine (Sec) and pyrrolysine (Pyl) are recognized as 21^st and 22^nd amino acids, respectively. tRNA^Sec and tRNA^Pyl have anticodon pairing with _______ and _______, respectively.
(A) UAA, CUG
(B) UGA, UAG
(C) UAA, UAG
(D) UAG, UGA
(E) UAG, UAA

84. Which DNA repair system is likely to be used in repairing DNA with an uracil residue? (A) Base-excision repair (B) Mismatch repair (C) Direct repair (D) Nucleotide-excision repair (E) Recombinational DNA repair

85. Aptamers are _______. (A) double-stranded RNA products of nuclease action on hairpin RNAs (B) repeat sequence elements at the ends of transposons (C) small RNA molecules selected for tight binding to specific molecular targets (D) the RNA primers required for retroviral replication (E) the short tandem repeat units found in telomeres

86. Which of the following modification elucidates the inhibitory effect of diphtheria toxin on the function of eukaryotic translation factor eEF2? (A) Phosphorylation (B) Dephosphorylation (C) ADP-ribosylation (D) Prenylation(E) S-Nitrosylation

87. Elongation factor Tu (EF-Tu): (A) binds GTP promoting translocation of ribosomes along mRNA (B) displaces GDP from the elongation complex (C) binds aminoacyl-tRNA in the presence of GTP (D) binds initiator tRNA and GTP (E) binds to 30S subunit and drives mRNA binding

89. Which step about regulation of gene expression by insulin is not correct? (A) Insulin receptor binds insulin and undergoes autophosphorylation. (B) Insulin receptor binds IRS-1 on its Tyr residues. SH3 domain of Grb2 binds to phosphorylated Tyr of IRS-1. (C) Sos binds to Grb2, then to Ras, causing GDP release and GTP binding to Ras. (D) Activated Ras binds and activates Raf-1. (E) Raf-1 phosphorylates MEK. MEK phosphorylates MAPK, activating it.

90Which description about β-adrenergic pathway (a G-protein coupling receptor; GPCR) is not correct? (A) The receptor is a 7-transmembrane protein. (B) Epinephrine binds to a GPCR. (C) The occupied receptor could cause the replacement of the GDP bound to GS (stimulatory G protein) by GTP, activating GS. (D) GSβ moves to adenylyl cyclase and activates it to synthesize cAMP. (E) cAMP activates PKA to trigger cellular response.

1. Rank the following monomers in order of increasing reactivity toward cationic polymerization (least reactive to most reactive). (A) III, IV, I, II (B) II, I, IV, III (C) I, II, IV, III (D) IV, III, I, II (E) I, II, III, IV

2. What product would be obtained for the following reaction?(A) CH3(CH2)3C≡CCH2OH (B) CH3(CH2)3C≡CCHO (C) CH3(CH2)3C≡CH (D) CH3(CH2)3C≡CNMe2 (E) None of the above.

3. Which two have the same molecular geometry? (A) I, II (B) III, IV (C) I, V (D) II, V (E) IV, V

4. Which nitrogen(s) have more basic? (A) I (B) II (C) III (D) I, II, and III are acidic (E) None of the above.