Gen371 Practice 1 Answers

Gen371 Practice 1 Answers - Gen371 Practice 1 Answers...

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1/26/11 4:18 PM Gen371 Practice 1 Answers Page 1 of 7 http://courses.washington.edu/au371mkr/resources/problems/problems_01-key.html Practice problems set 1 -- answers 1. The image you expect to see is the one showing RNA polymerases along the whole length of the gene, with RNA molecules of increasing size coming off the RNA polymerases: What's wrong with the other images? This one shows no RNA polymerases in the intronic region of the gene, as though the RNA polymerases were leaping across the intron portion and continuing to transcribe on the other side of the intron. Furthermore, RNA polymerases to the right of the intron suddenly have much larger RNAs hanging off them. RNA polymerases wouldn't jump across the intronic portion of the gene; the intron is part of the gene also and is transcribed as part of the same pre-mRNA. Here, the RNA molecules being transcribed are all different sizes as the polymerases traverse the gene. The RNAs get bigger starting at the left end of the gene, but then as the polymerases get into the intron portion the RNA molecules are suddenly short again,which doesn't make sense: as the RNA polymerase transcribes across the gene, the RNA molecule should keep getting bigger. In this version the RNA polymerases are present all across the gene, as we would expect, but the polymerases positioned over the intronic portion don't have RNA molecules. It's as though the RNA polymerases were releasing the RNAs when they got to the intronic portion and then recapturing the RNAs once they were on the other side -- which again is not how transcription works. The RNAs being made by the polymerases are small near the lefthand end of the gene and large near the right-hand end. Therefore, transcription must be starting at the lefthand end; that must be where the promoter is. 2. A 6-frame translation map of a segment of DNA is shown, with three open reading frames (A, B, and C). ORFs A and B are known to be in separate genes. Home Course mechanics Help hours Calendar Syllabus Lectures, Podcasts Quiz Sections Practice problems Exams GoPost Send email to class Useful links The Gradiator
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1/26/11 4:18 PM Gen371 Practice 1 Answers Page 2 of 7 http://courses.washington.edu/au371mkr/resources/problems/problems_01-key.html (a) Two transcription bubbles are shown, one in ORF A and one in ORF B. In the transcription bubble diagram, mark the following: the location of RNA polymerase on the appropriate strand in each bubble the RNA transcripts to show the relative lengths of RNA made by those two polymerases (b) Are the promoters for ORFs A and/or B present in the DNA region shown in this diagram? Promoter for A: Present? Yes No (circle one) If present, mark its location and label it. Promoter for B:
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Gen371 Practice 1 Answers - Gen371 Practice 1 Answers...

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