Card Set Information

2012-11-29 09:23:06

Show Answers:

  1. What is the central dogma and what are the exceptions to it?
    • DNA -> RNA -> protein
    • Exceptions can occur from reverse transcriptase
  2. Describe the process of transcription (including initiation, elongation, and termination)
    • RNA polymerase recognizes and binds to the promotor
    • DNA converted from ds to open structure
    • RNA polymease initiates RNA synthesis, no primer req
    • Chain elgonation occurs uder a core enzyme until it reaches a termination sequence [often forms a hairpin loop]
    • RNA molecule released
  3. What are the similarities and differences that exists between transcription in pro and euk re: promotor region and termination
    • pro promotor: located 5' region upstream from point of initial transcription.  Once RNA polymerase binds there the helix is denatured.
    • TATAAT: located 10 nucleotides upstream [pribnow box]
    • TTGACA: located 35 nucleotides upstream
    • euk promotor:
    • TATA box: located 35 nucleotides upstream [Hogness box]
    • CAAT box: located 80 boxes upstream
  4. What are the modifications are are required in pre-mRNA produced in eukaryotic cells before they can be shipped into the cytoplasm?
    • 5' cap: protects 5' end of molecule from nuclease attack, important to subsequent processing
    • 3' poly-A tail: protects RNA from degredation, critical for transport to cytoplasm
    • Removal of introns: via ssRNA or spliceosomes
  5. What are the different mechanisms available for splicing?
    • ssRNA: ribozymes. intron is removed, and RNA ligase joins the two remaining strands.
    • Spliceosome: huge molecular complex.  snRNA + proteins = snRNP.  snRNP forces intron into lariat and removes.  Exons are ligated and snRNPs released.
  6. What are the 4 major types of RNA that exist and what is the role of each?
    • mRNA: carries message between DNA and ribosome
    • rRNA: structural RNA for ribosome
    • tRNA: retrieves amino acids based on mRNA sequence
    • ribozymes: ribosomes with catalytic abilities (cleavage, ligation)