genetics transcription

  1. what subunit is responsible for promoter recognition?
    sigma unit of RNA polymerase
  2. what are the two consensus sequences in RNA polymerase and what are their placements?s
    TTGACA and TATAAT positioned at -35 and -10 with respect to transcription initiation site
  3. when does sigma component of RNA polymerase dissociate from the holoenzyme?
    after 8-9 nucleotides have been transcribed
  4. how do we know that genetic code was nonoverlapping?
    • point mutations only caused changes in one amino acid
    • more 16 combinations of three amino acids were possible were possible in the nonoverlapping sequence
  5. polycistronic
    encode multiple nonoverlapping proteins in mRNA
  6. what are the different types of RNA and what are their functions?
    • mRNA *coding
    • structural *rRNA
    • regulatory functions *miRNA
    • catalytic (ribozyme if within ribosome)
  7. what are segments of DNA that can be transcribed to RNA
    transcription units
  8. what is the role of RNA I
    rRNA in nucleolus
  9. what is the role of RNA pol II, and III
    • mRNA, snRNA for Pol II in the nucleoplasm
    • III= 5S RNA, and tRNA
  10. what is the TATA box
    • a core promoter element about 35 bp upstream of transcription start site that binds the TATA binding protein of transcription factor TFIID and determines the start of transcription
    • CAAT protein is 80bp upstream
  11. what is the role of enhancers
    it can modulate transcription from a distance, it may be upstream, down or within a gene
  12. what is the role of general transcription factors?
    they help RNA POL II bind to promoter and initiate transcription
  13. what precedes the ORF
    Untranslated 5'
  14. what are post-transcriptional modifications made to mRNAs?
    5' 7 methyl-gcap and polyA tail
  15. what are spliceosomes
    introns are spliced out of the primary transcipt (pre-mRNA)
  16. what is the insertion/deletion of RNA editing
    having uridines added to an individual transcript, usually forming the initial codon and then bringing the rest of the sequence into proper reading frames

    in trypanosomes it is directed by gRNA (guide RNA) templates. They base-pair with pre-edited mRNAs to direct the editing machinery to make the correct changes.
  17. what is substitution editing and what is a good example of this?
    where the identities of individual nucleotides are altered, changing the amino acid coding. apoliproteinB, changes codon to a stop codon
  18. what is the meaning of degenerate?
    more than one codon for some amino acids
  19. proteins are encoded by
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genetics transcription