DNA POLYMERASE

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DNA POLYMERASE

• By
• Jordan McGuire
• Jeremy Huynh
• Davis Grizzard
• Eric Halvorsen

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DNA POLYMERASEQuick Facts

• It is an enzyme
• The only task they are able to perform is adding
  nucleotides onto a pre-existing OH group
• made up of several different regions that
  function in roughly the same manner as the palm,
  thumb, and fingers of a human hand
• Proofreads as it binds base pairs

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• Simple version of DNA replication
• One strand of DNA enters the DNA polymerase and a
  full double helix is produced.

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DNA REPLICATION

• Helicase enzymes unwind the original double helix
  
• Single-strand binding proteins stabilize the
  unwound parental DNA
• On the leading strand, DNA polymerase comes in
  and synthesizes its new partner strand

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DNA REPLICATION (cont.)

• The other original strand, the lagging strand,
  must be synthesized
• Primase synthesizes a short RNA primer, which is
  extended by DNA polymerase to form an Okazaki
  fragment
• After the RNA primer is replaced by DNA, DNA
  ligase joins the Okazaki fragments to the growing
  strand

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DNA POLYMERASE aka HUMAN HAND

• the thumb and palm grasp the incoming
  single-stranded DNA and hold it securely in place
  
• the fingers, uses hydrophobic and hydrophilic
  interactions to rotate it and screen incoming
  nucleotides so that only the correct one can bind

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PROOFREADING

• Sometimes the incorrect base pair is used
• When the binding takes longer than normal, the
  DNA polymerase is alerted to the presence of an
  incorrect nucleotide and its correction
  mechanisms are activated
• The polymerase melts the last few nucleotides it
  had placed
• The fingers rotate and move the DNA so that it
  is able to resume placing nucleotides as far back
  along the strand of DNA as needed
• This proofreading takes place close to the center
  of the cell

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SIZE of DNA POLYMERASE

• Width of DNA 2.5nm
• Ribosome 20nm
• Hair 50,000nm
• DNA Polymerase lt42nm

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BACTERIAS DNA POLYMERASE

• 4 main types
• Pol I, which has a part in DNA repair and works
  in both ways along the DNA strand
• Pol II, which is involved in replicating damaged
  DNA and works in both ways
• Pol III, which is the main polymerase that works
  in the 3-5 direction and has proofreading
  ability
• Pol IV, which is a Y-family DNA polymerase.

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EUKARYOTESSDNA POLYMERASE

• 6 major types
• Pol a, which synthesizes the RNA primer and
  starts the elongation process using the DNA
  nucleotides
• Pol ß which is used in repairing DNA
• Pol ?, which replicates mitochondrial DNA
• Pol d and Pol e which work together as the main
  polymerase in eukaryotes and can also fill the
  gap after the primer has been removed
• And Pol ?
• There are also more than 6 other polymerases in
  eukaryotes

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E. COLI DNA POLYMERASE I