The History of DNA

1
The History of DNA

• TSW explain how the genetic code is contained
  within DNA
• TSW investigate the exploration of DNA structure

2
What is DNA?

• DNA stands for Deoxyribonucleic Acid
• DNA is present in the nucleus of all eukaryotic
  cells
• DNA controls all the chemical changes which take
  place in cells
• The kind of cell which is formed (i.e. muscle,
  blood, nerve, etc) is controlled by DNA
• The kind of organism which is produced (i.e.
  buttercup, giraffe, herring, human, etc) is
  controlled by DNA

3
DNA Molecule

• DNA is a macromolecule (i.e. Giant Molecule)
  made up of a long chain of sub-units (monomers)
  called NUCLEOTIDES
• Each NUCLEOTIDE has 3 main parts
• Phosphate Group (SUN)
• 5-Carbon Sugar (HOUSE)
• Nitrogenous Base (POOL)

4
Nucleotide Structure

• In DNA, the phosphate, DEOXYRIBOSE sugar, and a
  nitrogenous base combine to form a NUCLEOTIDE

5
DNAs Structure

• DNA is a double helix (think twisted ladder)
• 4 Nitrogenous Bases
• Adenine
• Thymine
• Guanine
• Cytosine

6
Nitrogenous Bases

• Purines
• Adenine (A)
• Guanine (G)
• Pyrimidines
• Thymine (T)
• Cytosine (C)

7
More DNA Structure

• Sugar-Phosphate backbone (sides of the ladder)
• Nucleotides held together by H bonds (rungs of
  the ladder)

8
Discovering DNA A Team Effort

• Frederick Griffith (1928)
• Question How do bacteria make people sick?
• Answer Transformation

9
Transformation

• Process in which one strain of bacteria is
  changed by a gene(s) from another strain of
  bacteria

10
Oswald Avery (1944)

• Question Which molecule is important for
  transformation?
• Answer DNA stores transmits genetic info from
  1 generation to the next

11
Hershey Chase (1952)

• Question Are genes made of DNA or protein?
• Experiment Which part of a bacteriophage enters
  the bacterium?
• Answer DNA

12
Hershey/Chase Experiment
13
Erwin Chargaff

• DNA base-pairing rules
• Adenine must pair with Thymine
• Guanine must pair with Cytosine
• Their amounts in a given DNA molecule will be
  about the same.

14
What does base-pairing look like?
15
Chargaffs Rule

• Remember Bases form the rungs on the DNA
  ladder by complementary pairing

16
Race for the Double-Helix

• Rosalind Franklin (1952) Used X-ray to determine
  that DNA is spiral-shaped
• Watson Crick (1953) Created 1st accurate model
  of DNA (double-helix), won the Nobel Prize

17
Draw the complementary strands

• CAGGCCTAC
• CATTGCAAG
• TAAGCGATA
• GCCATGAAT
• Dont forget Chargaffs Rule