DNA

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DNA Structure
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DNA Structure

• DNA consists of two molecules that are arranged
  into a ladder-like structure called a Double
  Helix.
• A molecule of DNA is made up of millions of tiny
  subunits called Nucleotides.
• Each nucleotide consists of
• Phosphate group
• Pentose sugar
• Nitrogenous base

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Cell
Chromosomes
Nucleus
Nitrogen Base Pairs
DNA
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Nucleotides
Phosphate
Nitrogenous Base
Pentose Sugar
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Nucleotides

• The phosphate and sugar form the backbone of the
  DNA molecule, whereas the bases form the rungs.
• There are four types of nitrogenous bases.

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Nucleotides
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Background

• We wish to suggest a structure for the salt of
  deoxyribose nucleic acid.
• So began a letter written to a scientific journal
  by two scientists in 1953 (American biologist
  James Watson and British physicist Francis
  Crick).
• In 1962, Watson and Crick (along with British
  scientist Maurice Wilkins) shared the Nobel Prize
  for physiology/medicine.
• Rosalind Franklin, whose research played an
  important part in unlocking the structure of DNA,
  did not share in the 1962 Nobel Prize.

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Franklin's Discovery
Rosalind Franklin, a British chemist, used a
process known as X-ray diffraction to make images
of DNA. Franklins images suggested that DNA has
a spiral shape. Based upon Franklins research,
Watson and Crick concluded that DNA looked like a
long, twisted ladder (or staircase).
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Opposites Attract
In the 1950s, a biochemist named Erwin Chargaff
found that the amount of adenine in DNA always
equals the amount of thymine. And he found that
the amount of guanine always equals the amount of
cytosine. His findings are known as Chargaffs
rules (at the time, no one knew the importance of
these findings).
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Nucleotides

• Each base will only bond with one other specific
  base.
• Adenine (A)
• Thymine (T)
• Cytosine (C)
• Guanine (G)

Form a base pair.
Form a base pair.
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DNA Structure

• Because of this complementary base pairing, the
  order of the bases in one strand determines the
  order of the bases in the other strand.

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DNA Structure

• To crack the genetic code found in DNA we need to
  look at the sequence of bases.
• The bases are arranged in triplets called codons.
• A G G - C T C - A A G - T C C - T A G
• T C C - G A G - T T C - A G G - A T C

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DNA Structure

• A gene is a section of DNA that codes for a
  protein.
• Each unique gene has a unique sequence of bases.
• This unique sequence of bases will code for the
  production of a unique protein.
• It is these proteins and combination of proteins
  that give us a unique phenotype.

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DNA
Gene
Protein
Trait
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Your Task

• Draw a flow chart to show how to get from