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Unformatted text preview: MCB121, C. S. Gasser MCB121 Problems on Transcription Regulation 1. Researchers studying transcription of a human gene constructed a set of plasmids containing various mutations in the promoter region of this gene. The plasmids were assayed to determine the level of transcription in both an in vitro system (containing partially fractionated human cell nuclear extracts), and in transgenic cells using polyethylene glycol-mediated transformation. The following data were obtained, with a level of 1 representing transcription from the unmutated promoter in each system (even though the level of transcription was at least 10-fold higher in vivo than in vitro): a) (6) What types of sequence elements are likely to be in the promoter near positions 25 and 75 where mutations seem to have strong affects in both systems? 25 : 75 : b) (3) In which of the two assays is transcription more affected by mutations near position 50? (circle correct answer) In vitro In vivo c) (8) Based on what you know about transcription, propose an explanation for the difference in effects of mutations near position 50 between the two experiments. 0.5 1.0 0.5 1.0 Relative Transcription Rate +1-25-50-75-100 Location of mutation (bases from transcription start) In vitro In vivo MCB121, C. S. Gasser 2. A B C D. An activation domain E. An enhancer element In each of the blanks below, write the one letter from among the five choices above that best matches what is described. One letter per blank, but each letter may be used for more than one blank. Helix-loop-helix Arg Arg Phe Ser Arg Ser Asp Glu Leu Thr Arg His Ile Arg His Thr Gly Gln Lys Pro Phe Gln Cys Arg Ile Cys Met Arg Asn Phe Ser Arg Ser Asp His Leu Thr His Ile Arg Thr Asn His Thr Gly Glu Lys Pro Phe Ala Cys Asp Ile Cys Gly Arg Lys Phe Ala Arg Ser Asp Glu Arg Lys Arg His Thr Lys His Leu Arg Gln Lys Asp 5'-TGACGTCA-3' Lys Ala Glu Lys Arg Met Arg Asn Arg Ile Ala Ala Ser Lys Cys Arg Lys Arg Lys Leu Glu Arg Ile Ala Arg Leu Glu Glu Lys Val Lys Thr Leu Lys Ala Gln Asn Ser Glu Leu Ala Ser Thr Ala Asn Met Leu Arg Glu Gln Val Ala Gln Leu Lys Gln Gln Glu Gln Thr Pro Gln Arg Gln Gln Asn Gln Thr Ser Gly Gly Ser Leu Gln Ala Gly Gln Lys Glu Gln Asn Gln Gln Thr Gln Gln Gln Gln Ile Leu Ile Gln Pro Gln Leu Val Gln Gly Gly Gln Ala Leu Gln Ala Leu Gln MCB121, C. S. Gasser 2. A B C D. An activation domain E. An enhancer element In each of the blanks below, write the one letter from among the five choices above that best matches what is described. One letter per blank, but each letter may be used for more than one blank....
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- Winter '09