Friday, February 10, 2012
DNA from green peas!
1. Gather together a packet of green split peas, detergent, salt , meat tenderizer,alcohol (we used hand sanitizer), a seive,blender,jug and small jar
2. Put in the blender:
• split peas
• 1/8 teaspoon table salt (less than 1ml)
• 1 cup cold water (200ml)
Blend on high for 15 seconds.(The blender separates the pea cells from
each other, so you now have a really thin pea-cell soup.)
Add 2 tablespoons liquid detergent (about 30ml) and swirl to mix.
Let the mixture sit for 5-10 minutes.
Pour the mixture into test tubes or other small glass containers, each about 1/3 full.
4.Add a pinch of enzymes to each test tube and stir gently. Be careful! If you stir too
hard, you’ll break up the DNA, making it harder to see.
Use meat tenderizer for enzymes. (If you can’t find tenderizer, try using pineapple
juice or contact lens cleaning solution.)
5.Tilt your test tube and slowly pour rubbing alcohol (70-95% isopropyl or
ethyl alcohol):( remember the handsanitizer!) into the tube down the side
so that it forms a layer on top of the pea mixture. Pour until you have about the
same amount of alcohol in the tube as pea mixture.
Alcohol is less dense than water, so it floats on top. Look for clumps of white
stringy stuff where the water and alcohol layers meet.
6.DNA is a long, stringy molecule. The salt that you added in step one helps it stick
together. So what you see are clumps of tangled DNA molecules!
DNA normally stays dissolved in water, but when salty DNA comes in contact with
alcohol it becomes undissolved. This is called precipitation. The physical force of
the DNA clumping together as it precipitates pulls more strands along with it as it rises
into the alcohol.
You can use a wooden stick or a straw to collect the DNA. If you want to save your
DNA, you can transfer it to a small container filled with alcohol.