25. Dr. Roger Komberg (Stanford University) used structural basis to reveal the mechanism of        nucleotide selection       in the posttranslocation state of eukaryotic RNA polymerase II. Which of the following statement is       not true      ?
(A) The study reveals two distinct nucleotide-binding sites, the E and A sites, at the active center of RNA polymerase II
(B) The E site is the location where incoming nucleotide first encounters
(C) The A site is the location where phosphodiester bonds form
(D) Rotation of nucleotide between the E and A sites may be helpful for base specificity
(E) Rotation of nucleotide between the E and A sites may be affect the specificity for deoxyribonucleotides as opposed to ribonucleotides

複選題21. Which of the following statement is       true      ? (A) Eukaryotic RNA polymerase III makes tRNAs and snRNAs (B) Rpbl of yeast RNA polymerase is homologous to alpha-subunit of bacterial RNA polymerase (C) Rpb5 of yeast RNA polymerase II is also a component of RNA polymerase I and III (D) Zipper is a protein loop within eukaryotic RNA polymerase II and is involved in initiating dissociation of the RNA-DNA hybrid (E) Yeast RNA polymerase contains 10 apparent subunits and four of them are phosphorylated

22.Which of the following statement is       not true       for eukaryotic gene promoters? (A) For the promoters recognized by RNA polymerase II (class II promoters), TATA-less promoters are commonly found in housekeeping and developmentally regulated genes (B) Initator is required for optimal transcription of some class II promoters; one classic example is the adenovirus major late promoter (C) Class I promoters (the promoters recognized by RNA polymerase I) are quite variable in sequence across species, while they all contain a conserved AT-rich initator (rINR) (D) Some of the class I promoters are located entirely within the genes themselves, one example is the 5S rRNA gene (E) Some of class III promoters (the promoters recognized by RNA polymerase III) resemble those found in class II genes, one example is the 7SL gene

23. Please predict the possible consequence of blocking the       action of TFIIF      , a general transcription factor of RNA polymerase II. (A) The TFIIDAB complex will not form (B) Polymerase may not bind to the DAB complex (C) TFIIA will not bind to TFIID (D) The TFIIDAB complex will not form and TFIIA will not bind to TFIID (E) Transcription elongation is enhanced by limiting nucleotide misincorporation

24. Which of the following statement is       true      ? (A) TFIID is the factor enhances transcription elongation by limiting transcription arrest (B) TFIIA is the general transcription factor of RNA polymerase II that can determine the start site and direction of transcription (C) TFIIH is the general transcription factor of eukaryotic RNA polymerase II that contains the helicase activity and involves in promoter clearance (D) TFIIF is a main component of TFIID with a saddle-like shape (E) TAFII250 is one of the human TATA binding protein (TBP)-associated factors and contains a phosphotase activity to dephosphorylate TFIIE

26. Which of the following statement related to the nuclear receptor is       not true      ? (A) Thyroid hormone receptor belongs to type I receptors, which stay in the cytoplasm in the absence of its ligand (B) Type III receptors are "orphan" receptors whose ligands are not yet identified (C)In the presence of ligand, the glucocorticoid receptor (GR) can form a homodimer within the nucleus (D)In the absence of ligand, GR exists as an inactive form in cytoplasm complexed with the heat shock protein 90 (Hsp90) (E) Nuclear receptors interact with different endocrine-signaling molecules and activate gene expression via its binding to hormone response DNA elements

27. Predict the consequence of treating the 70S ribosomal with urea: (A) the RNA portion would be degraded. (B) the unit would be undisturbed. (C) the protein component would be degraded. (D) the unit would dissociate RNA and protein components. (E) the treatment would lead to tighter association between RNA components.

28. Which of the following is not part of the 30S initiation complex? (A) IF1, IF2, and IF3 (B) 5S rRNA (C) 16S rRNA (D) amino-acyl tRNA (E) mRNA

29. Picornavirus mRNAs are not capped, yet they can still out compete host mRNAs for binding to the ribosome by (A) having a stronger affinity for the ribosome. (B) degrading host mRNA. (C) inactivating host Cap binding protein, eIF4F. (D) inactivation of host RNases. (E) inactivation of host Cap binding protein, eIF2B.

30. EF-Tu is an important protein in cells whose function is to (A) properly fold proteins. (B) ensure proper ribosome assembly. (C) escort aminoacyl-tRNA to the ribosome. (D) protect rRNA from degradation by RNases. (E) stabilize mRNA within the ribosome. 

1. A Double-stand DNA can be peeled off by a _____ to become 2 single-strand DNAs. (A) DNA polymerase (B) helicase (C) RNA polymerase (D) ligase