B2: DNA

Nota:

• Function of DNA = instruction for body to make protein

1. Structure of DNA

   Nota:

   • Double helix.  Sugar phosphate backbones, two strands twisted together.  4 complimentary bases joined by weak hydrogen bonds.  Bases only pair: A+T and C+G
   1. Adenine
   2. Thymine
   3. Cytosine
   4. Guanine
2. Discovery of DNA
   1. Rosalind Franklin and Maurice Wilkins

      Nota:

      • Studying DNA using x-ray crystallography (1950s London).  Patterns recorded allowed Rosalind Franklin to work out how the groups of atoms in the DNA were arranged (double helix). 
   2. James Watson and Francis Crick

      Nota:

      • Watson & Crick used x-ray results to build a 3D model of the DNA structure without permission.  Eventually contributions made by Franklin and Wilkins became clear and Wilkins, Watson and Crick won the Nobel Peace Prize in 1962 for discovering structure of DNA.  Franklin died 4 years earlier aged 27.