Intro to DNA

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Intro to DNA

• DNA Deoxyribonucleic acid
• -double polymer of nucleotides
• -SS chromosomes contain 1 molecule of DNA (re
  double polymer of nucs)
• -after DNA replication, a DS chromosome contains
  2 complete polymers of DNA
• -sequence of nucleotides of DNA codes for
  sequence of amino acids of protein (process
  referred to as protein synthesis)
• -protein synthesis DNA ? RNA ? Protein
• - The pathway of protein synthesis is also
  referred to as the Central Dogma of Molecular
  Biology

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DNA is a polymer of nucleotides

• A nucleotide contains three essential parts
• 5 carbon sugar
• Deoxyribose in DNA
• Ribose in RNA
• Nitrogenous base
• Adenine, Guanine purines
• Thymine, (Uracil), Cytosine pyrimidines
• Phosphate group

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Components of nucleotide structure
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Single polymer of DNA nucleotides
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Events leading to DNA model proposed by Watson
and Crick (1953)

• Chargaffs rules
• the proportion of As in DNA the proportion of
  Ts
• The same holds true for Gs and Cs
• Franklins X-ray diffraction photos
• Suggested DNA was helical and perhaps contained
  two separate chains of nucleotides separated by a
  discrete diameter
• Watson/Crick model fit the available data
• Each backbone of alternating sugar phosphate
• Each backbone has a polarity in that each is
  oriented in the opposite direction
• Complementary base pairing between purine and
  pyrimidine
• A binds to T (forming 2 H bonds)
• G binds with C (forming 3 H bonds)
• Model suggested a mechanism of DNA replication
  and of protein synthesis

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DNA structure with double polymer of DNA
nucleotides showing antiparallel orientation of
complementary nucleotide strands
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Basics of DNA replicationreplication is via
semi-conservative model
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Basics of DNA replication

• The DNA helix unzips exposing the 2
  single-stranded parental templates of nucleotides
• New nucleotides are added against each exposed
  nucleotide in a complementary fashion
• Since the enzyme which completes this task
  reads the DNA in only 1 direction, it affects
  the process of DNA replication

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The replication process
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The replication process
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The replication process
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Replication process with major enzymes included
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Replication of lagging strand