U07_F08 - Unit 7 1 UNIT 7 PART A: RNA STRUCTURE AND...

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Unit 7 1 U NIT 7 P ART A: RNA S TRUCTURE AND F UNCTION P ART B: T RANSCRIPTION P ART C: C O - AND P OST -T RANSCRIPTIONAL M ODIFICATION OF RNA P ART D: T RANSCRIPTIONAL C ONTROL OF P ROTEIN S YNTHESIS P ART A: RNA S TRUCTURE AND F UNCTION In eukaryotes, DNA is largely confined to the nucleus, whereas protein synthesis occurs on ribosomes in the cytoplasm. In the early 1950's, it was found that the onset of protein synthesis was accompanied by an increase in the amount of RNA in the cytoplasm. RNA carries the genetic information from DNA to the protein biosynthetic machinery of the ribosome in the cytoplasm. Assignment: Nelson & Cox, review pp. 271 - 273, 283 - 287. 1. Describe the function of each of the following (p. 271): a. rRNA b. mRNA c. tRNA
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Unit 7 2 2. Compare DNA and RNA with respect to: a. Identity of the pentose ring (ribose vs deoxyribose; Fig. 8-1, p. 271). b. Which nitrogen bases (C,A,G,U, and/or T) are found in DNA? In RNA? (Fig. 8-2, p. 272) 3. Distinguish between monocistronic and polycistronic mRNA (p. 284). Is eukaryotic mRNA monocistronic or polycistronic? What about prokaryotic mRNA? 4. Secondary structure (pp. 284 - 286) a. Is DNA usually double or single stranded? b. Is RNA usually double or single stranded (p. 284)? Does single stranded RNA have any double stranded regions? Using Fig. 8-23 (p. 285) to illustrate your answer, point out a hairpin loop (sometimes called a stem and loop). Within double-stranded regions of RNA, define two types of base pairs. Note: The molecule shown in Fig. 8-24 (p. 285) has much more secondary structure than would be found in a typical messenger RNA. 5. Tertiary Structure: Note what RNA structures actually look like (Fig. 8-25, p. 286, x-ray structures).
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Unit 7 3 P ART B: T RANSCRIPTION Replication and transcription differ in one important respect. During replication the entire chromosome is copied to yield daughter DNAs identical to the parent DNA. Transcription, in contrast, is selective. Only particular genes or groups of genes are transcribed at any one time. The transcription of DNA can be regulated so that only genetic information needed by the cell at a particular moment is transcribed. Specific regulatory sequences indicate the beginning and end of the segments of DNA to be transcribed, as well as which DNA strand is to be used as the template. Assignment: Nelson & Cox pp. 1021 - 1031. 1. Use Fig. 26-1 (p. 1023) to give an overview of transcription by RNA polymerase. Distinguish between RNA polymerases and DNA polymerase I in terms of : a. Substrates b. Whether a primer is needed c. The direction of synthesis (3' 5') or (5' 3') d. The nucleophilic attack in bond formation e. The role of pyrophosphate and pyrophosphatase in the overall reaction f. The requirement for a template 2. What is meant by the terms "template" and "non-template" strands
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U07_F08 - Unit 7 1 UNIT 7 PART A: RNA STRUCTURE AND...

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