ExamII-06 - page1...

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page 1 Bio 324 Molecular Biology Exam II November 14, 2006 1. a. In transcription, one of the two DNA strands is copied into RNA. Is the same DNA strand used to sythesize all RNAs in the cell, or are different RNAs copied from different DNA strands? (3 pts.) b. In prokaryotes, the promoter is defined as the region of DNA contacted by RNA polymerase. Why is this definition not appropriate for eukaryotic promoters? (3 pts.) c. The core bacterial RNA polymerase has a high affinity for non-specific DNA sites. How does association with the sigma subunit change the affinity of the RNA polymerase for both non-specific and promoter sequences? (3 pts.) d. Hexameric sequences centered at -10 and -35 bp upstream of the start point are critical for proper transcription. If I were to introduce 10 extra bp between the two hexamer consensus sequences, but not change their base sequence, would you expect this to affect the activity of the new promoter? Explain your reasoning. (3 pts.) e. There are two types of transcriptional terminators in bacteria, intrinsic and rho dependent. What is the structure of an intrinsic terminator and how does this structure result in termination. Is the termination signal recognized as a DNA or RNA sequence? ( 3 pts.) 2. a. Eukaryotes use three different RNA polymerases to transcribe different sets of promoters. For RNA polymerases I, II and III, which types of genes are transcribed by each? ( 3pts.) b. The 5S RNA genes of X. laevis (frogs) are transcribed by RNA polymerase III. When all of the DNA sequence upstream of +1 is deleted, transcription still
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ExamII-06 - page1...

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