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From DNA to Protein Chapter 7 -- Transcription and Translation

This chapter explores the key events in the process of transcription and translation, including the role of RNA polymerase, promoters, consensus sequences, RNA processing, and the structure and function of ribosomes and tRNAs. The chapter also discusses the RNA world hypothesis and the evidence supporting it, as well as the reasons for the evolutionary selection of DNA as the repository for genetic information.

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From DNA to Protein Chapter 7 -- Transcription and Translation

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  1. From DNA to Protein Chapter 7 -- Transcription and Translation There are several good animations on the The Virtual Cell web site  watch them Questions in this chapter you should be able to answer: Chapter 7- #s 2 - 14, 16A,C,D, 17 From DNA to Protein

  2. There are many steps between DNA & Protein From DNA to Protein

  3. What are the key events during transcription? Begins at Promoter Ends at terminator σ-factor is required in prokaryotes Transcription Jmol-RNA polymerase From DNA to Protein

  4. What is a promoter? For example, in prokaryotes… Consensus sequences σ-factor Orientation Initiation site Jmolσ-factor on DNA Virtual Cell Animation From DNA to Protein

  5. Transcription in Eukaryotes is more complex Two concepts for now… • 3 RNA polymerases RNA polymerase I RNA polymerase II RNA polymerase III 2) General transcription factors Some bind to “TATA-box” 5’-TATAAA-3’ consensus sequence  initiation complex Some bind to RNA polymerase II  polymerase phosphorylation From DNA to Protein

  6. Either strand may carry template sequence Question 7-2 In what direction are the RNA polymerases moving in this image? Another question: From an evolutionary perspective, why don’t overlapping genes occur? From DNA to Protein

  7. What happens to mRNA after (as) it is transcribed? Capping RNA processing Polyadenylation Export Translation From DNA to Protein

  8. What is 5’ capping and polyadenylation? Poly-A tail protects against RNAse (function is sort of like a telomere) From DNA to Protein

  9. How does RNA processing occur? snRNPs, Spliceosomes and Ribozymes RNA Processing From DNA to Protein

  10. Is an mRNA always processed in the same way? -- “alternative splicing” -- can be very complex… From DNA to Protein

  11. How do mRNAs get to the cytosol? Only properly processed RNAs allowed out Why doesn’t this process involve importins and nucleoporins that we discussed earlier? From DNA to Protein

  12. What is the structure of the ribosome? What are the functions of the A, P & E sites? Jmol - Ribosome From DNA to Protein

  13. What is the structure of tRNAs? Anticodon 3’ AA binding site ‘Charging’ How many tRNAs? -- 48 in humans -- wobble allows some to fit 2 or more codons tRNA model From DNA to Protein

  14. How is translation initiated? Orientation Initiation complex Finding start codon Add LSU Translation From DNA to Protein

  15. How does elongation and termination proceed? Passing of peptide From P- to A-site tRNAs Ribosome translocation Release factor Elongation Polyribosome From DNA to Protein

  16. RNA and the evolution of Life Why RNA as start of evolution? 1) Has genotype & phenotype 2) Could have self-replicated From DNA to Protein

  17. What is the evidence for the RNA world? Central roles of ribonucleotides -- m-,t- r-RNAs -- ribozymes -- ribosome catalysis -- miRNAs -- telomerase -- ATP, NADH, etc Experimental demonstrations From DNA to Protein

  18. Why did DNA evolve as the repository for genetic information? Why is it genetically more stable? Why is it chemically more stable? From DNA to Protein

  19. Why does DNA contain thymine instead of uracil? From DNA to Protein

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