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Unformatted text preview: BIO320-Spring 2010 Question bank B 1 mkernan 2010 REGULATING GENE EXPRESSION IN PROKARYOTES SIGMA PROTEINS 1. One way that bacteria can tailor their gene expression to changing conditions is by activating different sigma proteins. Genes activated by different sigma proteins probably have different: A) translation initiator codons B) operator sequences C) core RNA polymerases D) ribosome binding sites E) promoter sequences OPERON STRUCTURE & REGULATION 2 . Which of the following statements about the structural genes in the lac operon of E. coli is false : A) The genes are closely linked on a recombination map. B) The gene products perform different functions in a single biochemical pathway. C) The genes are transcribed into a single polycistronic transcript. D) The genes are translated into a single polyprotein which is then cleaved into separate proteins. E) The genes are coordinately regulated. 3. Fill each gap in the following sentence with either the word "one" or the word "several": "A typical polycistronic bacterial operon has ____ promoter(s), ______transcription start site(s), ____transcription stop site(s), _____translation start site(s), _____ long open reading frame(s), and ________ translation stop site(s)." 4 . A bacterial operon encodes several enzymes that together convert amino acid X into amino acid Z, which is essential for growth. Would you expect expression of this operon to be... A. Repressed in the presence of amino acid X. B. Repressed in the presence of amino acid Z. C. Repressed in the absence of amino acid Z. D. Activated (derepressed) in the absence of amino acid X. E. Activated (derepressed) in the presence of amino acid Z. 5. Repressor proteins can recognize specific DNA segments because of contacts made between: A. Peptide bonds in the protein and the ribose rings in the DNA B Amino acid side chains in the protein and the bases in the the DNA C. Amino acid side chains in the protein and the phosphates in the DNA D. The amino terminus of the protein and the 5 end of the DNA E. The carboxy terminus of the protein and the 3 end of the DNA 6 . When the lac repressor binds an inducer, it undergoes an allosteric shift. Is this likely to change its: A. primary structure B. secondary structure C. tertiary structure D. (A, B and C) E. none of the above 7. Which of the following statements about bacterial repressors is FALSE? A) Repressors have separate sites for binding to DNA and other ligands. B) Repressors must be encoded on the same DNA molecule as the genes they regulate. C) Binding an inducer decreases the affinity of a repressor for its operator. D) Repressors prevent transcription when bound to DNA. E) Binding a corepressor increases the affinity of a repressor for its operator....
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- Spring '10