HOW TO EXTRACT DNA FROM ANYTHING LIVING

DNA Extraction: Since DNA is the blueprint for life, everything living contains DNA. For this explanation, we will use green split peas. This could be done with any other DNA sources, such as: Spinach Chicken liver Strawberries Broccoli Skin Cells

Certain sources of DNA should not be used, such as: Your family pet, Fido. Your little sister. Bugs you caught in the yard. You don’t do this “just because.”

Step 1: Blender This step is only necessary with plant cells. Put the following into a blender: 1/2 cup of split peas (100ml). 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, and breaks up the cell walls. So, you now have a really thin pea-cell soup.

Why add salt? What is its purpose? Salty water helps the DNA precipitate (solidify and appear) when alcohol is added later.

Why is cold water better than warm water for extracting DNA? Cooling slows down enzymatic reactions. This protects DNA from enzymes (Dnases) that can destroy it. These enzymes are present in the cell’s cytoplasm to destroy the DNA of viruses that may enter our cells and make us sick. A cell’s DNA is usually protected from such enzymes by the nuclear membrane. •

Step 2: Strain Pour your thin pea-cell soup through a strainer into another container. This is to separate the particles of cell wall from the freed-up cells.

Step 3: Soap / Detergent Add 2 tablespoons liquid detergent (about 30ml) and swirl to mix. Let the mixture sit for 5-10 minutes.

Why Do I Add These To My Pea Soup Mixture? Each cell is surrounded by a cell membrane. DNA is then found inside a second membrane that creates the nucleus within each cell. To see the DNA, we have to break open these two membranes. We do this with detergent or soap.

Why soap? How does it work? Think about why you use soap to wash dishes or your hands. To remove grease and dirt, right? Soap molecules and grease molecules are made of two parts: They organize themselves in bubbles (spheres) with their heads outside to face the water and their tails inside to hide from the water.

When soap comes close to grease, their similar structures cause them to combine, forming a greasy-soapy bubble.

A cell's membranes have two layers of lipid (fat) molecules with proteins passing through and floating among them.

When detergent comes close to the cell, it captures the lipids and proteins, destroying the cell membrane.

Step 4: Enzymes Add a pinch of enzymes to each test tube and stir gently. Not too hard. In this experiment, meat tenderizer acts as an enzyme to cut proteins just like a pair of scissors. At this point the tube is sometimes placed in a hot water bath, but not always. •

We use meat tenderizer for enzymes We use meat tenderizer for enzymes. If you can't find tenderizer, try using pineapple juice or contact lens cleaning solution.

The enzymes cut away the histone proteins to free-up the DNA.

Step 5: Heat (Optional) This step does not show up in all protocols, but it can be affective in helping to disrupt the cell and nuclear membranes even further by denaturing the proteins found suspended between them. Place the tube in a hot water bath (55 – 60 degrees C) for 10 minutes.

Step 6: Centrifuge Centrifuge in a balanced centrifuge, at low to medium speed. Carefully remove the tube from the centrifuge. Note the two phases within it: Upper layer: supernatant, DNA is dissolved here. This needs to be saved. Lower layer: pellet, cell debris, discard it.

Step 7: Decant. Decant the supernatant, avoiding any of the pellet. Remember – keep the supernatant. If purity of DNA is important, the supernatant should be pipetted off with a wide bore pipette.

Step 8: Alcohol Separation Tilt your test tube and slowly pour either rubbing alcohol (70-95% isopropyl) or ethyl alcohol into the tube down the side so that it forms a layer on top of the supernatant. Pour until you have about 10 mL.

Alcohol is less dense than water, so it floats on top 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.

How long will my DNA last? Will it eventually degrade and disappear? DNA may last for years if you store it in alcohol in a tightly-sealed container. If it is shaken, the DNA strands will break into smaller pieces, making the DNA harder to see. If it disappears it’s likely because enzymes are still present that are breaking apart the DNA in your sample.

What can be done with my extracted DNA? This sample could be used for gel electrophoresis, for example, but all you will see is a smear. The DNA you have extracted is genomic, meaning that you have the entire collection of DNA from each cell. Unless you cut the DNA with restriction enzymes, it is too long and stringy to move through the pores of the gel. A scientist with a lab purified sample of genomic DNA might also try to sequence it or use it to perform a PCR reaction. But, your sample is likely not pure enough for these experiments to really work.