Protein Synthesis

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Protein Synthesis
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DNA mRNA
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DNA

• Cannot the nucleus
• Sends to the cytoplasm via
• Its base sequence (called a codon) determines
  the amino acid in proteins
• DNA and acts as a template for synthesis of
  mRNA ( RNA)

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mRNA

• Base sequence is to DNA
• 3 base sequences (called ), which are to the
  triplet codons in DNA determines the amino acid
  sequence in proteins
• Travels from the to the
• Process through which is formed from is
  called

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Transcription

• Initiation
• RNA polymerase the DNA to find a region
• Once it finds the region, the polymerase will
  the DNA and will begin to at a slow rate
  (about 10 nucleotides)

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Transcription

• Elongation
• Once the promotor region is (transcribed) the
  RNA polymerase will begin a highly processive
  transcription process in the to direction
  (approx. bases/second)
• The base pairing is as follows
• Adenine in RNA will pair
• Cytosine in RNA will pair
• Uracil in RNA will pair
• Guanine in RNA will

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Transcription

• Termination
• A rich region at the end of the gene causes
  hydrogen bonds and so the RNA polymerase complex
  off, terminating translation

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mRNA amino acids

• translation

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rRNA

• Ribosomes are made up of ( RNA) and proteins
• The ribosome has a structural purpose in protein
  synthesis, where it hosts translations
• mRNA codons are read and specific tRNAs are
  signalled

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tRNA

• tRNA RNA
• Is made up of
• Found the in the cytoplasm
• Attaches to in the cytoplasm and the amino
  acid to ribosome
• Each tRNA has a 3 base sequence called the and
  this sequence mRNA at the ribosome

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Translation

• Initiation
• mRNA finds the ribosome and forms a
• The first moves into place as the
  on the find and attach to the codons on the
  mRNA in the ribsosome
• The first codon always reads known as the
  codon

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Translation

• Elongation
• As mRNA shifts along ( by ), new molecules
  bring in amino acids to the
• The amino acids on the join (via peptide bond)
  to form a chain

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Translation - elongation
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Translation

• Termination
• Eventually, the ribosome will read a codon on
  the mRNA
• The stop codon does not code for any , and so
  the chain will be released from the
• The is also released and returned to the nucleus
  to be broken down into nucleotides, if needed

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Protein Synthesis

• Protein synthesis is now . The polypeptide
  chain is to act as a protein or be combined with
  other polypeptide chains to form a .

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Proteins 4 levels of organization
The amino acid sequence determines the
three-dimensional structure of a protein The
structure of a protein determines the proteins
function
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Summary
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Determine the AA sequence
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By the end of this section you should be able to

• Identify the roles of DNA, messenger RNA (mRNA),
  transfer RNA (tRNA), and ribosomes in the
  processes of transcription and translation,
  (including initiation, elongation, and
  termination) of Protein synthesis
• Determine the sequence of amino acids coded for
  by a specific DNA sequence (genetic code), given
  a table of mRNA codons
• Identify the complementary nature of the mRNA
  codon and the tRNA anti-codon