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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.