Republic of the Philippines
Department of Education
MIMAROPA Region
Division of Romblon
PERFORMANCE TASK NO. ___
IN EARTH AND LIFE SCIENCES (2ND QUARTER)
Name: Date:
Grade Level/Section: Score:
DNA Isolation from Your Cheek Cells
Objective:
Isolate Deoxyribonucleic Acid (DNA) strands from human cheek cells
Materials:
Salt solution (dissolve 8 g of salt in 92 ml of bottle of distilled water)
Liquid dishwashing detergent solution (mix 25 mL of liquid detergent to 75 mL distilled bottled
water)
Plastic drinking cup Ethyl alcohol (95% denatured)
Test tube with stopper 3 droppers
Test tube rack Glass stirring rod
Distilled bottled water
Estimated Time Frame: 1 hour
Procedure:
1. Pour 10 mL of distilled water in a clean plastic drinking cup.
2. Before performing this step, do not brush your teeth or gargle water so as not to interfere with
the procedure. Put 10 mL of water into your mouth and swirl the water around for at least one
minute A longer period of time and more violent swirling will cause more cells to be sloughed-
off. Spit the water back into the plastic cup.
3. In a test tube, add 1 mL (approximately 20 drops) of salt solution.
4. In the same test tube (in no. 3), add around 5 mL of the spitted water.
5. Add 1 mL (20 drops) of liquid dishwashing detergent solution. Detergents will break down the
lipids and proteins found in the cell membrane thereby disrupting the cells and releasing the
6. DNA into the salt solution.
Note: The action of the detergent can be enhanced by placing the test tube in water at 55 C. This will
also denature the enzymes that might damage DNA.
7. Cover the test tube with a stopper and mix the contents of the tube gently by inverting the test
tube five times. Do not shake the test tube.
8. Holding the test tube in a slightly angle (around 45 degrees), slowly add 5 mL of ethyl alcohol
down the side of the test tube so that it forms a layer over the cell lysate mixture (mixture of
disrupted cheek cells).
Note: Ice cold ethyl alcohol might be more effective to precipitate DNA.
9. Gently hold the test tube upright and observe what happens at the interface between the ethyl
alcohol and cell lysate mixture. Observe the clouds of white strands at the interface. Those are
the DNA strands! DNA is insoluble in ethyl alcohol so it precipitates where the two liquids
meet. Soap bubbles will get trapped in the DNA strands.
10. Collect the DNA strands by placing in clean glass stirring rod in the test tube and turning it in
one direction (spooling). The DNA strands will wind around the glass stirring rod.
11. Carefully lift the rod with the DNA and transfer it into a new test tube containing 1 mL (20
drops) of ethyl alcohol. Observe the DNA strands floating in the ethyl alcohol.
CARMEN NATIONAL HIGH SCHOOL “The Glimmer of Hope”
Carmen, San Agustin, Romblon
School ID: 309205
e-mail: 309205@deped.gov.ph
Republic of the Philippines
Department of Education
MIMAROPA Region
Division of Romblon
Observations:
1. Describe the strands of DNA you have isolated.
2. Compare the DNA strands you isolated with those of your classmates. Describe the possible
factors that influenced the differences in the observed DNA strands.
3. Draw the setup done during the collection of the DNA strand with the glass string rod.
Conclusion:
Post-Laboratory Questions:
1. With the action of detergents learned from this experiment, describe the potential harm the
practice of disposing large amount of detergents into the bodies of water has on aquatic organism.
2. Give the possible scenarios wherein DNA isolation and analysis is useful.
Prepared by:
KEYAM NIEL B. RACE Noted:
Subject Teacher
JUDITH F. FABELLON
School Principal III
CARMEN NATIONAL HIGH SCHOOL “The Glimmer of Hope”
Carmen, San Agustin, Romblon
School ID: 309205
e-mail: 309205@deped.gov.ph
