Transcription and Translation Exam 3

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Transcription and Translation Exam 3
2013-12-14 16:15:17
biology exam
biology exam 3 final
Show Answers:

  1. central dogma
    DNA -> RNA -> Protein
  2. Transcription
    DNA to RNA (mRNA)
  3. Stages of Transcription
    • 1.Initiation - recognize promoter region 
    • 2.Elongation - make a RNA copy 
    • 3.Termination - split from DNA
  4. direction of transcription
    which one it copies varies but will always copy from 5' - 3' (DNA will be facing 3' to 5')
  5. RNA processing
    • Bacterial mRNAs can be used immediately Eukaryotic mRNAs  need to be cut and add cap and a tail
    • Introns- spliced
    • Exons- expressed
  6. splicing
    via splicesome (made of SnRNP)

    rRNA and tRNA are self splicing via ribozymes
  7. capping
    guanocine* added on 5' end NEEDED for mRNA to exit the nucleus
  8. Poly A tail
    • Adenine added to the 3'
    • Increases stability and lifespan in cytosol
    • Not encoded in gene sequence
  9. codon
    mRNA base triplets
  10. template strand
    DNA strand that will be turned into mRNA
  11. Degenerate
    more than one codon can specify the same amino acid

    • 20 amino acids 
    • 1 codon 1 amino acid but 64 possible codons
  12. translation
    mRNA to protein
  13. tRNA
    • clover structure (but L shaped b/c of hydrogen)
    • has anticodon that matches the codon 
    • acceptor stem for amino acid binding
  14. Aminoacyl-tRNAsynthetase
    • Catalyzes the attachment of amino acids to tRNA
    • Reactions result in tRNA with amino acid attached or charged tRNA or aminoacyl tRNA
  15. Ribosome
    • ribosomal subunits (large and small) made of rRNA
    • ribosome shape determined by rRNA

    E (Exit), P (Growing Poplypeptide), A (Acceptor),  sites
  16. Stages of Translation
    • 1.Initiation - mRNA, first tRNA and ribosomal subunits
    • assemble
    • 2.Elongation - Synthesis from start codon to stop codon
    • 3.Termination - Complex disassembles at stop codon
    • releasing completed polypeptide
  17. Bacteria
    • mRNA binds to small ribosomal subunit
    • facilitated by ribosomal-binding sequence
    • Start codon a few nucleotides downstream
    • Initiator tRNA recognizes start codon in
    • mRNA
    • Large ribosomal subunit associates
    • At the end, the initiator tRNA is in the
    • P site
  18. wobble
    3rd base in codon can be switched some and still make the same amino acid
  19. AUG
    start in eukaryotic cells
  20. Stop codons
    terminate transcription
  21. polyribosome
    translate a single mRNA simultaneously

    make copies of polypeptide quickly
  22. Targeting the Functional Protein
    polypeptide is modified after translation and completed protein target specific sites in the cell
  23. free and bound ribosomes
    • free ribosomes make protein that function in cytosol
    • bound make protein in ER that will be secreted from the cell 

    they can switch!
  24. random protein info
    • •Polypeptide
    • synthesis always begins in the cytosol

    • •Synthesis
    • finishes in the cytosol unless the
    • polypeptide signals the ribosome to attach to the ER

    • •Polypeptides
    • destined for the ER or for secretion are marked by a signal
    • peptide