DNA Extraction from vege and humans

Nexus Research Group - FUN Science and home experiments...: "To isolate plant DNA

* blend 50g of Cauliflower in 200 mL of water for 30 seconds to get single cells.
* Strain through muslin cloth. Pour 15 mL of liquid into a screw cap tube with 3 drops of detergent and shake gently for 5 seconds.
* Carefully layer to top of tube with cold alcohol (or meths). Use a hooked glass rod to spool out strands of DNA at the interface.

To isolate your own human DNA

(an original protocol independantly developed by Nexus, please acknowledge our contribution if using this protocol for teaching purposes)

* To a 1/2 cup of water dissolve about 1/2 teaspoon of salt and add a squirt of dish-washing detergent. Save this for step 3
* Swirl about 25 mls of water around your mouth for 30 seconds. This removes some cheek cells. Spit into a disposable cup
* Add about 2cm of the fluid to a test-tube (or a Fuji film cannister) and add about 1cm of the saline/detergent solution. Invert gently 3 or 4 times to mix well (but you don't want a lot of froth). This will break open the many cheek cells you spat out, releasing the DNA message that each cell must carry.
* Layer on top some ice cold ethanol (or methanol). Strands of DNA will be seen where the two layers meet. Hook out the strands of DNA that form with a glass hook (or one made from a plastic twist-tie) by slowly dipping up and down through the two layers.


The following chemical tests can be used to check you actually have DNA:

* Test for purines: Add excess 2M ammonia solution and a few drops of 0.1M silver nitrate to 1 mL of DNA extract. A white precipitate indicates the presence of purines.
* Test for phosphate: Add 1 mL of 0.2M ammonium molybdate (39.02g/L) to 0.5 mL of extracted DNA and warm gently at 60-70oC. DO NOT BOIL. Yellow colour indicates presence of phosphate.
* Test for deoxyribose: Add 2 mL of Disches reagent to 1 mL of extracted DNA. Boil in water bath for 15 minutes. Green-blue colour indicates presence of deoxyribose. Disches reagent: 486 mL glacial acetic acid, 14 mL conc. sulphuric acid, 5g diphenylamine. Stir well and add 500 mL distilled water"