Card Set Information

2011-10-13 23:16:45
dna rna transcription

prokaryotic and eukaryotic transcription
Show Answers:

  1. 3 phases of transcription
    initiation, elongation, termination
  2. template for transcription
    a single strand of DNA
  3. Substrates for transcription
  4. Which direction does RNA synthesis proceed?
    5'->3', just like everything else...
  5. What's the difference between DNA and RNA polymerases?
    RNA polymerases have no other associated activities, like proofreading.
  6. What part(s) of the RNA polymerase is required for elongation in prokaryotes?
    only the core enzyme
  7. What part(s) of the RNA polymerase is required for initiation?
    the holoenzyme, which is the core enzyme plus the additional sigma subunit
  8. purpose of nuclear RNAs
    to synthesize different RNAs
  9. How many and what type of RNA polymerases do eukaryotes have?
    one mitochondrial and three nuclear RNA pols. The three nuclear RNA pols have different sensitivities to amanitin
  10. True/false: Both DNA and RNA synthesis requires a primer
    False. RNA synthesis (aka transciption) does not require a primer.
  11. Which nuclear RNA is very sensitive to amanitin and what does it make?
    • II
    • hnRNA (=mRNA) and some snRNAs
  12. Which nuclear RNA is moderately sensitive to amanitin and what type of RNA does it make?
    • III
    • tRNA; 5S rRNA, 7S RNA, and some snRNAs
  13. Which nuclear RNA is insensitive to amanitin and what type of RNA does it make?
    • I
    • 45S rRNA
  14. Which type of eukaryotic rRNA is the product of transcription of a different gene and which nuclear RNA makes it?
    • 5S RNA
    • III
  15. How does RNA polymerase know where to start transcription?
    Promoter sequences, which differ between prokaryotes and eukaryotes, direct them.
  16. 3 sequence elements for most prokaryotic promoters
    • initiation site
    • Pribnow box
    • -35 sequence
  17. What type of nucleotide is the initiation site usually?
  18. What makes the promoters used by RNA pol III in eukaryotes unique?
    They usually start downstream of the startpoint.
  19. What makes RNA pol II promoters unique?
    There is a large diversity of them.
  20. What sequence elements are common to RNA pol II's?
    • TATA box
    • CAAT box
    • GC box
  21. Affect the rate of initiation of transcription but are not actually considered promoter elements because they don't affect the accuracy of initiation of transcription
  22. What is required for accurate initiation of transcription in prokaryotes? In fact, it is the only initiation factor needed in these organisms.
    sigma factor
  23. What's the function of the sigma factor?
    Enables RNA polymerase holoenzyme to recognize and bind tightly to the promoter sequences
  24. What does the sigma factor actually do?
    It faciliates the opening or melting of the DNA double helix.
  25. What is the mechanism of action of Rifampin?
    • It binds to the beta subunit of RNA polymerase when it's still in holoenzyme form.
    • By doing so, it inhibits the initiation (not elongation!) of transcription in bacteria.
    • Rifampin has no effect on eukaryotic nuclear RNA polymerases, thus making it an effective antiobiotic.
  26. Sequences that cause termination transcription by forming a stable stem-loop structure through self-complementary sequences.
    factor-independent termination
  27. True/false: In factor-independent termination, there is a specific place where termination stops.
    FALSE. RNA pol just falls off at some point on the uracil segment.
  28. How does rho bind at unique termination sequences?
    as a hexamer
  29. What type of enzyme is rho?
    an ATPase
  30. What does it mean to say that rho is an ATPase?
    Rho cleaves ATP in the process of termination, although the exact mechanism is unknown.
  31. 2 methods of termination in prokaryotes
    • factor-independent termination
    • rho
  32. How does RNA pol I terminate transcription?
    factor-dependent mechanism
  33. How does RNA pol III terminate transcription?
    by an unknown mechanism after the synthesis of a series of U's
  34. How does RNA pol II terminate transcription?
    We don't know.
  35. Remove spacer RNA in the 30S precursor rRNA in prokaryotes.
    • ribonuclease P
    • ribonuclease III
  36. In addition to the removal of the spacer sequences, some of the bases in the final rRNAs of prokaryotes are _____, which is necessary for the rRNAs to be functional.
  37. Sequence common to all tRNAs
    CCA sequence on 3' end
  38. What's the name of the enzyme that adds the CCA sequence onto tRNAs that have been left without it after cleavage from the larger precursor transcript?
    tRNA nucleotidyl transferase
  39. Where does the synthesis and processing of 45S rRNA begin? What enzyme does this?
    • nucleolus
    • RNA pol I
  40. precursor for eukaryotic rRNA
  41. precursor for eukaryotic mRNA
  42. 2 functions of caps on eukaryotic mRNA
    • more efficient translation
    • more stable mRNA
  43. A complex of proteins that recognizes and binds to the cleavage/polyadenylation signal
    Directs an endonucleolytic cut of the RNA to a particular point downstream
    cleavage and polyadenylation specificity factor
  44. Joins the cleavage and polyadenylation specificity factor complex and, after the RNA is cut, catalyzes the polymeration of A residues onto the 3' end of the mRNA
    poly A polymerase
  45. When does polyadenylation occur?
    After capping but before splicing
  46. Function of polyadenylation
    helps stabilize mRNA
  47. the transcribed portions of the gene that are retained in the final mRNA product
    exons (short for expressed)
  48. What catalyzes splicing?
    a spliceosome
  49. Function of snRNAs in the spliceosome
    recognize the conserved sequences by introns and bringing together the RNA sequences into perfect alignment for splicing.
  50. How does tRNA splicing work?
    The splicing enzymes recognize characteristic structural features of the tRNA to recognize specific intron/exon junctions.