Fruit DNA extraction (strawberry, banana, or kiwi)

Where to buy & price

Just examples of where to look and roughly what to expect to pay, get everything from wherever works for you, at whatever price you find.

Strawberries/bananas, Naivas, Quickmart, Chandarana, or any open-air market, bananas ~KSh 10–20 each, strawberries ~KSh 150–300/punnet. Dish soap ~KSh 100–150. Table salt ~KSh 30–50/500g. Rubbing alcohol/surgical spirit, Goodlife Pharmacy, MYDAWA, Carrefour, Nila Pharmaceuticals (100ml Rosapharm surgical spirit sold at Carrefour Kenya; 5L container KSh 999 at Tiba Quip Africa, buy the smallest size available).

Cold storage / timing

Freeze the alcohol for 10–15 minutes before use, a real requirement, not optional (NIH's genome.gov: "the colder the rubbing alcohol, the less soluble the DNA will be in it").

Reagents & materials required

Procedure, step by step

1. 1

   Place your fruit in a ziplock bag and mash it thoroughly by hand for 1–2 minutes, until it's a smooth pulp with no large chunks.

2. 2

   Mix an extraction buffer in a separate cup: 2 tablespoons of dish soap, 1 teaspoon of salt, and 1 cup of water. Stir gently, avoid making a lot of foam.

3. 3

   Add 2–3 tablespoons of the extraction buffer to the mashed fruit in the bag, reseal it, and mash gently for another minute to mix them together.

4. 4

   Filter the mixture through a coffee filter or a layer of cheesecloth into a clear cup or test tube, collecting only the liquid and discarding the solids.

5. 5

   Tilt the tube and slowly pour cold rubbing alcohol down the inside wall so it forms a separate layer floating on top of the fruit extract, use roughly the same volume of alcohol as extract.

6. 6

   Let it sit undisturbed for 1–3 minutes and watch the boundary between the two layers, white, stringy, cloudy material forming there is the precipitated DNA.

7. 7

   Use a wooden skewer or toothpick to gently spool the DNA strands out for a closer look, then photograph your result.