Exam 4

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jordanmcqueen
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56454
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Exam 4
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2010-12-16 02:17:28
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Exam 4
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  1. Gene expression
    • the process by which DNA directs protein synthesis,
    • includes two stages:

    • –Transcription
    • (mRNA synthesis)

    • –Translation (polypeptide, or protein,
    • synthesis)
  2. Transcription
    • copying
    • think of medical transcriptionist
    • The synthesis of RNA under the direction of DNA
    • Produces messenger RNA (mRNA)
  3. Translation
    • think languages: language of nucleotides to language of amino acids
    • The actual synthesis of a polypeptide
    • Occurs under the direction of mRNA
    • Occurs on ribosomes
  4. Codons
    nonoverlapping base triplets of genetic information
  5. RNA synthesis
    • Catalyzed by RNA polymerase (pries the DNA strands apart and hooks together the RNA nucleotides)
    • works 5’-3’, but doesn’t need a primer like DNA polymerase does
    • Follows the same base-pairing rules as DNA, except that in RNA, uracil substitutes for thymine
  6. Transcription (stages)
    • Initiation
    • Elongation
    • Termination
  7. Promoters
    • signal the initiation of RNA synthesis
    • RNA polymerase binds to promoter, DNA strands unzip, transcription commences
  8. Post-Transcriptional Modification of RNA
    • The 5' end receives a modified nucleotide cap
    • The 3' end gets a poly-A tail
    • RNA splicing removes introns and joins exons, forming the final mRNA molecule which now exits the nucleus, entering the cytoplasm
  9. Exons
    the sequences that will be translated into protein
  10. tRNA
    translates an mRNA message into protein in a ribosome
  11. Ribosome
    • 2 Subunits
    • E site (Exit site)
    • A site (Aminoacyl-tRNA binding site)
    • P site (Peptidyl-tRNA binding site)
  12. Mutations
    Changes in the genetic material of a cell
  13. Point mutations
    Changes in just one base pair of a gene

    • –Base-pair substitutions
    • –Base-pair insertions or deletions
  14. Mutagens
    Physical or chemical agents that can cause mutations
  15. carcinogens
    cancer-causing chemicals
  16. histones
    Proteins responsible for the first level of DNA packing in chromatin and binds tightly to DNA

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