Explanation of DNA Extraction

All living things, both plants and animals, contain DNA (deoxyribonucleic acid) that determines the characteristics inherited by their descendants. No two living things, except twins that came from one separated ovum, or egg cell, contain identical DNA. Extracting a sample of DNA for laboratory analysis sounds complicated. Laboratories do use sophisticated equipment, but surprisingly, anybody can extract DNA with household products.

Form

• DNA is a nucleic acid that contains genetic instruction and information. It comes in the shape of a spiraling strand of two separate, ladder-like strands called nucleotides that contain the genetic code. These ribbons of DNA must be extracted if they are to be studied and compared.

Breaking Open the Sample

• To extract DNA, the biological sample first needs to be broken open. Laboratories do this with special machines that vibrate the sample at high speeds.

  At home you can use a blender. You can extract DNA from cockroaches or grass from your front yard. Add a half cup of sample and a pinch of salt to a cup of water and blend for 15 seconds at high speed. The salt will eventually help turn the liquid DNA into a solid form, called a precipitate.

Separating the DNA Nucleus

• Each living cell is surrounded by a lipid membrane, a kind of sack. Inside this sack is a second lipid membrane. The second sack contains the DNA that you're after. You need to separate these two sacks. A detergent will do that. Laboratories use a variety of chemicals to do the same thing. Strain your sample, add two tablespoons of detergent and let stand for five to ten minutes. Put this mixture into test tubes or other glass containers, each about one-third full.

Freeing the Nucleus

• The nucleus of the DNA is protected by proteins that are molded and folded around it. To separate this nucleus, you need to cut through the protective layer of proteins. You do that with enzymes. Meat tenderizer, pineapple juice, or the solution that cleans contact lenses will give you the necessary enzymes. Add a pinch of meat tenderizer to each test tube and stir gently. Laboratories have numerous sophisticated varieties of enzymes at their disposal.

Turning Liquid DNA into Solid DNA

• Your DNA is now in a liquid form. DNA remains dissolved in water.

  DNA does not dissolve in alcohol. Alcohol will cause DNA to come together in a solid form, a process called precipitating. As it does this, the alcohol will remove the salt that you previously added.

  Slowly pour rubbing alcohol (70 to 95 percent ethyl or isopropyl alcohol) down the inside of your test tube or other container. When you have a mixture that is 50 percent water and 50 percent alcohol, stop.

  Long, stringy molecules of DNA will begin to rise toward the alcohol. As they do, the strands will come together, forming stringy clumps. You'll see them collect where the water meets the alcohol.

  You have successfully extracted DNA.

  Laboratories ordinarily use a centrifuge to speed up this stage, but the result is the same.

  You can use a straw to collect the DNA that you can examine under a microscope if you like.

DNA Confirmation

• Laboratories use ultraviolet light to better see the DNA. They use a fluorescent die that reacts with DNA or a gel that contains ethidium bromide.