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QB08-B - BIO320-Spring 2008 Question bank B REGULATING GENE...

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BIO320-Spring 2008 Question bank B 1 mkernan 2008 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. A polycistronic message, such as that transcribed from a bacterial operon, may have A. A single promoter but several transcription start sites. B. A single transcription start site but several open reading frames. C. A single translation start codon but several stop codons. D. Several transcription start sites and several stop codons. E. Several promoters and several open reading frames. 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: 6 . When the lac repressor binds an inducer, it undergoes an allosteric shift. Is this likely to change its:
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