Friday, 10 January 2014

DNA Extraction from Strawberries

Three strawberries lovingly squished by hand to break down the cell walls of the strawberry.
Strawberries are octoploid, meaning that they contain 8 copies of each chromosome.
Human cells are diploid, meaning that they contain 2 copies of each chromosomes.

To half a cup of (cool) de-ionized water add 2 squirts of fairy liquid, 1 tsp of salt, the strawberry pulp, and a small splash of pineapple juice (a few drops). Do not stir. Well you can slosh it about a bit, but don't stir it.

  • Detergent acts as a lysis buffer which breaks open the membrane enclosing the cell and the nuclei membranes within the cells.
  • Salt makes the DNA precipitate (solidify and appear) when the alcohol is added later.
  • Pineapple Juice contains an enzyme known as bromelain which is a protease, meaning that it breaks apart proteins.

DNA is thus released into the solution.

Without stirring, filter the liquid. Reserve just a small amount of the liquid.

(Because if you have too much liquid in your final cup you might find you don't have enough alcohol to go around. And you need as much alcohol as the filtered liquid for this. And god knows you probably only have a finite amount of alcohol.)

Add the same amount of isopropyl alcohol to the liquid. Do not stir.

DNA precipitates when in the presence of alcohol, which means DNA is not soluble / does not dissolve in alcohol. Fish it out with a stick.

Strawberry DNA can now be transferred to an Eppendorff Tube for storage. This 'spool' of DNA is actually a mix of DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), so the entire process can also be described as nucleic acid extraction.

Thanks to Raphael Kim and Johanna for guiding us through this and other experiments in the workshop.

All notes above are mine own, do let me know if there are any inaccuracies on the role of each ingredient or step.

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