Bio Exam 3 Study Questions

Bio Exam 3 Study Questions - George Fountain III Team:...

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George Fountain III Team: Golden Retrievers EXAM 3 STUDY QUESTIONS (Version 1, 11/03/09) The questions on the third hour exam will be based on those given below.  If you can answer  them, you should have little trouble with the questions on the exam.  [Note:  These questions are  meant to provoke thought and study.  As before, do  not  ask me or any of the TAs to provide you  with the answers.] 1. What does a “promoter sequence” do in bacteria? What are the two “boxes” and why are they important? What is the role of the sigma factor? There is typically more than one type of sigma factor in most species of bacteria. Why? In bacteria, a “promoter sequence” Transcription begins when sigma, as part of the holoenzyme complex, binds to the - 35 and -10 boxes. Once it is bound to a promoter, sigma opens the DNA helix and threads the template strand through the enzyme’s active site. When transcription is under way, sigma disengages from RNA polymerase. The sigma factor tells RNA polymerase where and when to start synthesizing RNA. 2. What happens during the “elongation phase” of transcription? How does transcription end? During the elongation phase of transcription, RNA polymerase moves along the DNA template in the 3’ to 5’ direction of the template strand, synthesizing RNA in the 5’ to 3’ direction. Transcription ends with a termination phase, which is when RNA polymerase reaches a stretch of DNA sequence that functions as a transcript termination signal. The formation of the hairpin structure disrupts the interaction between RNA polymerase and the RNA transcript, resulting in the physical separation of the enzyme and its product. 3. In eukaryotes there are at least three different RNA polymerase enzymes. What does each of them do? What would the result be if there was a deletion mutation in RNA pol I, RNA pol II, or RNA pol III? How does the initial mRNA transcript differ in eukaryotes and bacteria? RNA polymerase I - genes that code for most of the large RNA molecules found in ribosome RNA polymerase II - protein-coding genes- produce mRNAs RNA polymerase III - genes that code for transfer RNAs and genes that code for one of the small RNA molecules found in ribosome. Deletion mutation involves the loss of genetic material. p. 1
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4. Eukaryotic mRNA that leaves the nucleus and enters the cytoplasm has been processed in a number of ways. What happens during “splicing” and why is splicing needed? What feature(s) of the mRNA that enters the cytoplasm make the mRNA last longer? During splicing the introns are removed from the primary RNA transcripts and the remaning exons are connected together. With the addition of the cap and tail processes the primary RNA transcript and
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This note was uploaded on 01/22/2011 for the course BIO 100 taught by Professor Sokolove during the Fall '08 term at UMBC.

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Bio Exam 3 Study Questions - George Fountain III Team:...

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