Transcription

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Transcription

• Review

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Prokaryotes
RNA polymerase Transcription Prokaryotic
promoters Consensus sequence
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Promoters Gene Regulation

• RNA polymerase binds to promoter initiating
  transcription
• (may have strong or weak
  promoters)
• binding of the RNA polymerase can be prevented or
  assisted by other regulatory proteins that bind
  to operators, adjacent to or within the promoter.
• ability of these regulatory proteins to bind to
  the DNA is often dependent upon being bound to an
  effector.
• regulatory proteins may control transcription of
  more than one promoter -- simultaneous control of
  several different cell functions.

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Elongation
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Eukaryotic transcription

• Euks have 3 RNA Pols in nucleus
• Type I rRNA
• Type II mRNA (snRNA)
• Type III tRNA

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Eukaryotic transcription
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(No Transcript)
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Translation
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• A messenger RNA is "read" (translated) by a
  ribosome/tRNA machine. The reading of the
  information is accomplished by the recognition of
  the genetic code.

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The Open Reading Frame

• An open reading frame is the sequence of codons
  from (and including) the start codon (usually
  AUG) to the stop codon (UAG, UAA, or UGA).
• mRNA have 3 reading frames
• CCCAUGUUUCCCGGGAGGCUU

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• CCCAUGUUUCCCGGGAGGCUU
• -CCC AUG UUU CCC GGG AGG CUU
• pro met phe pro gly arg leu
• C CCA UGU UUC CCG GGA GGC UU
• pro cys phe pro gly gly
• CC CAU GUU UCC CGG GAG GCU U
• his val ser arg glu ala

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(No Transcript)
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The Genetic Code

• All 64 codons have been assigned
• 61 code for amino acids
• 1 CODES FOR START SIGNAL AUG-sets the reading
  frame
• 3 (UAA, UAG, and UGA) serve as termination
  signals
• only Trp and Met have one codon each
• the third base is irrelevant for Leu, Val, Ser,
  Pro, Thr, Ala, Gly, and Arg
• the second base is important for the type of
  amino acid for example, if the second base is U,
  the amino acids coded for are hydrophobic
• for the 15 amino acids coded for by 2, 3, or 4
  triplets, it is only the third letter of the
  codon that varies. Gly, for example, is coded for
  by GGA, GGG, GGC, and GGU

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• Codon base triplet on mRNA
• anticodon base triplet on tRNA
• tRNAs can recognize multiple codons (mRNAs)-
  why?gtgt WOBBLE
• Wobble (variation)
• Affects 3rd base of codon and 1st base of
  anticodon
• Anticodon base is always U, G, or I (inosine)
• A and C do not exhibit wobble

Fig 11.4
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Protein Synthesis

• Figure 11.17 Simultaneous protein synthesis on
  polysomes