The stuff of life Biology Mrs. Kathy

Process and Procedure You will learn that you can extract DNA from various foods that are found in your refrigerator.

Materials Blender, dish detergent, toothpicks, meat tenderizer, small glass containers, rubbing alcohol and strainer.

Step 1 1. Measure out 1 cup of water, ¼ cup of peas and ¼ tsp of salt. Stir until salt is dissolved. Leave the peas in water until softened. I have soaked the peas overnight to soften them for you. 2. Put the peas and the salt water in the blender and chop for a couple of seconds. You may use a fork to squash the peas. The mixture should be lumpy, containing small pieces of peas. Too much blending will break up the DNA and make it too hard to see. 3. Gently mix the peas and water from the blender with few drops of soap in the glass container.

Step 2 1. Put the pea mixture in the strainer. 2. Filter about 1/3 cup of the liquid into a small glass container. 3. Wet the end of a toothpick and dip it into the meat tenderizer. 4. Put the end with the enzymes in the cell mixture and gently stir.

Step 3 1. Slowly pour in an equal amount of the rubbing alcohol ( about 1/3). 2. The alcohol should form a layer on top of the cell debris. 3. Watch carefully as the DNA precipitates through the alcohol. The DNA is clear. Small bubbles will attach to the strands as they migrate up through the alcohol. Use the toothpicks to gently stir the alcohol layer. Notice how those strands move like snot. The snotty substance is the DNA.

Questions Now that you extracted DNA from peas, think about each step of the procedure and why it worked. 1.How did each of the ingredients in the experiment help extract DNA from the other parts of the cell? 2. What part of the cells would be most affected by soap? 3. What is it in meat tenderizer that breaks down meat? 4. Alcohol and salt: Why does only the DNA and not the other parts of the cell, rise to the top after addition of alcohol?

Answers 1. Blending will separated the pea cells. But each cell is surrounded by a sack ( the cell membrane). DNA is found inside a second sack ( the nucleus) within the cell. To be able to see the DNA we have to break open these 2 cells. 2. Think about why you use the soap to wash your hand, to remove grease and dirt correct! Soap molecules and grease molecules are made of 2 parts. Both soap and grease molecules organize themselves in bubbles with the heads of the bubble outside to face the water and their tails inside to hide from the water. When soap comes to close to grease their similar structures cause them to combine forming a greasy soapy ball.

Cont. answers 3. Meat tenderizer breaks down the bonds between the amino acids. 4. DNA does not break up in rubbing alcohol.