DNA As A Data Storage Medium

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DNA As A Data Storage Medium
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Molecular Genetics DNA as a replicating molecule
Textbook Readings Ch. 16-background only Ch.
17-most important Ch. 19 Sec. 19.1 also
important Ch. 18 and 20-not yet Ch. 15 (reminder)
Secs. 15.3-15.5
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Molecular Genetics DNA

• Four roles for DNA
• Information storage
• Replication (reproduction)
• Day to day instructions to the cell
• Mutation

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Molecular Genetics DNA replication-an overview

• DNA replication
• Precedes cell division.
• Process overview
• DNA strands separate
• New complementary base pairs are added forming a
  new strand
• Result
• two double helices (daughters)
• Each includes one old strand of DNA and one new
  strand of DNA (semiconservative)

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Molecular genetics-DNA replication is
semi-conservative

• Half of the original double helix is conserved in
  each daughter double helix
• All cells operate this way but some viruses do
  not
• Dont rely on this cartoon for accuracy-the new
  strands (black) are not growing in the right
  direction

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Molecular genetics-DNA replication is
enzyme-catalyzed

• No step takes place spontaneously
• Every step is regulated by an enzyme
• The replication machine is called the replisome
• The spot where the replisome is working is called
  the replication fork
• The enzymes that actually make new DNA are called
  DNA polymerases. Several types are required (in
  addition to other enzymes).

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Molecular genetics-DNA replication requires
unwinding of DNA

• Helicase is the protein that unwinds DNA
• Requires ATP energy

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Werners syndrome-a helicase-associated human
disorder

• Recessive
• Inability to repair DNA
• and maintain telomeres
• Premature aging
• Arteriosclerosis
• Diabetes mellitus

WS is considered a form of progeria
by some scientists
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Question

• Each base-pair of DNA is about 0.00000134 inches
  long. If there are 6 billion base pairs in the
  genome of a single human cell, how long would the
  cells DNA be if stretched out end to end?

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Molecular genetics-DNA polymerase has a big
problem

• In all known cells DNA polymerases can work in
  one direction only. Unfortunately the DNA to be
  replicated runs in two directions.

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DNA polymerase must replicate in two directions

• Due to antiparallel structure of the double helix
• The enzyme, unfortunately, is not that flexible
• 5 to 3 synthesis only

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The solution

• The two strands of the double helix are
  replicated differently
• Leading strand-continuous replication
• Lagging strand-discontinuous (backstitching)
• Has to take place at same replication fork