Protein Synthesis

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Protein Synthesis

• The Molecule of Life
• Transcription and Translation

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Transcription and Translation

• Transcription begins the process of protein
  synthesis
• Translation results in the end protein molecule
• Several organelles in the cell are involved

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Cell Organelles Involved in Protein Synthesis
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Transcription Start of Protein Synthesis

• Where?
• Nucleus in Eukaryotes
• Cytoplasm in Prokaryotes
• What?
• Many cell organelles involved
• RNA Polymerase plus some minor proteins
• DNA code becomes encoded in mRNA

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Transcription Start of Protein Synthesis

• When?
• When RNA is needed
• Why?
• RNAs serve many important functions in cells
• RNA encodes protein sequences
• How?

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Transcription Defined

• Transcription to transfer a code into another
  code
• ie. To rewrite one language into another

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Where are we?
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Transcription

• How?
• mRNA made 5?3 directionality
• DNA unzips only at a specific gene sequence for a
  specific protein
• Usually only one strand of DNA is read to form a
  complementary copy of the mRNA

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Transcription

• Uses Base-pairing but U instead of T pairs with
  A.
• RNA nucleotides float into place with the aid
  of RNA polymerase and complementary base pairing
  occurs
• There are nonsense codes at the end of the gene
  that terminate mRNA synthesis.
• mRNA breaks off and moves out of the nucleus into
  the ribosomes of the cytoplasm
• Same idea as with DNA replication
• Transcription Animation
• Transcription translation - fast

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Transcription Layout

• 5 end RNA
• 3end RNA

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mRNA Enters Cytoplasm
http//www.dnatutorial.com/RNATranscriptionAnimati
on.shtml
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Translation

• What?
• mRNA? Protein molecule
• Where?
• Cytoplasm
• Ribosomes are main organelles

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Translation

• When?
• When proteins are need, after mRNA is made
• Why?
• Proteins are vital for cells
• Enzymes, tissues, hormones, cell structure all
  require proteins

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The Genetic Code
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Translation Defined

• Translation to interpret a code into meaning.
• In biology The process by which messenger RNA
  directs the amino acid sequence of a growing
  polypeptide during protein synthesis.

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Proteins Structure and Function

• Amino acids connect to form small chains called
  peptides, which get larger and form polypeptides.
• There are 20 amino acids useful to humans
• We consume these in our diet, our body makes a few

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Proteins Structure and Function

• In anabolism, our body needs to assemble these
  amino acids into specific protein structures. A
  missing amino acid means an entire protein cannot
  be madethe RNA cannot fill the hole left by
  its absence
• A.A. allow the protein molecule to form its
  necessary structure
• Proteins have many structures/shapes

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Peptide Bond Formation Dehydration Synthesis
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From Amino Acid to Protein Structure
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The Big Question?

• How do amino acids assemble themselves correctly?

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Translation

• How?
• Ribosomal Subunits
• Small subunit
• Large subunit
• Codon on mRNA
• Triplet nucleotide code used
• Each triplet codes for a specific tRNA attached
  to a specific amino acid

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Translation

• How?
• mRNA, tRNA, rRNA are all used

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A couple definitions

• CODON
• a triplet of nucleotides on the mRNA
• Triplet codes for a specific tRNA complementarity
• The codon is the genetic code
• ANTICODON
• A triplet of nucleotides on the bottom of the
  tRNA
• Triplet anticodon complements the mRNA codon
• tRNA brings a specific amino acid

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The Genetic Code
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Test for Understanding the code

• A DNA sequence has the following bases T A C - A
  G A - T T A - G G G - A T T What amino acids
  does it code for? (You'll need to use the codon
  chart)

• mRNA CODONS
• AUG UCU AAU CCC UAA
• Metser asn pro-stop
• AUG usually is START
• UAA is STOP
• Amino acid sequence is actually SER-ASN-PRO
• tRNA each has one specific amino acid and this is
  how amino acids know the sequence of attachment
  !

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Recall tRNA

• Anticodon attaches to codon
• Amino acid valine is attached to this specific
  tRNA
• Valine will always attach to tRNA with the same
  anticodon
• Amino acid binding site is amino acid specific

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Summary

• Translation
• DNA Rap
• protein synthesis
• Protein Transport

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Why is this important?

• Genetic Engineering
• Gene Splicing
• Mutations
• Cloning
• http//www.johnkyrk.com/DNAtranscription.html
• Castle Analogy

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Mutations

• Point Mutations
• Single base change
• Base-pair substitution
• Silent mutation
• No AA change
• Missense
• AA change
• Nonsense
• Stop codon change
• When do mutations affect the next generation?

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A Mutations leads to Sickle Cell Anemia

• What kind of mutation?

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Sickle Cell Anemia
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Mutations

• Frameshift
• Shift in reading frame
• Changes everything downstream
• Insertion
• Adding a base(s)
• Deletion
• Losing base(s)
• Which is more harmful point or frameshift?