The Discovery of DNA structure
- It was in 1962 when James Watson and Francis Crick along with Maurice Wilkins were awarded a Nobel Prize for discovering the structure of DNA.
- In the 1950s, in London, Rosalind Franklin and Maurice Wilkins used X-Ray photography to study the shape size of a DNA molecule. They found DNA had a helical structure.
- In Cambridge James Watson and Francis Crick use data from many studies including Franklin and Wilkins’ results to build a 3D model of DNA showing its double helix structure.
- They used Franklin’s best images without asking her permission. It was these details in her images that gave Watson and Crick the clues they needed to build their double helix model.
- When Watson and Crick published their paper on DNA their reference to the London team was only a footnote. Unfortunately, Rosalind Franklin died at age just 37 4 years before she could receive her rightly deserved Nobel prize.
Extracting DNA from cells
- Chop up some onion and put it in a beaker containing a solution of detergent and salt. The detergent will break down the cell membranes and the salt will make the DNA stick together.
- Put the beaker into a water bath at 60⁰C for 15 minutes as this denatures the enzymes that could digest the DNA and help soften the onion cells.
- The beaker must be put into ice to cool down quickly which stops the DNA from breaking down.
- When the mixture is ice-cold, it should be put into a blender for a few seconds to break open the cell walls and release (but not break up) the DNA.
- Cool the mixture down again, and then filter it to get the froth and big bits of cell out.
- Ice-cold alcohol should be added slowly to the mixture. The DNA will start to come out of the solution as it’s not soluble in cold alcohol. It will appear as a stringy white substance.