Genomic DNA Isolation (from human cheek cells)
Summary
In this lab activity students isolate genomic DNA from their cheek cells on the inside of their mouths. Students then remove the DNA from those cheek cells. It shows the DNA is in every cell in the body and can be extracted easily. Students use their DNA necklace which they proudly wear around school the rest of the day.
CollapseLearning Goals
1. This lab is designed to introduce students to the concept of DNA controlling living organisms.
2. The difference between mitochondrial and genomic DNA.
3. Accurate measurement and following directions.
KEY CONCEPTS
1. DNA, the genetic material of organisms, is composed of four kinds of nucleotides.
2. DNA is a molecule which consists of two strands with sugars and phosphates on the outside and nitrogen base pairs on the inside held together by weak hydrogen bonds.
Vocabulary Words
DNA (mitochondrial and genomic)
nucleotide
nitrogen base pairs
lysis
2. The difference between mitochondrial and genomic DNA.
3. Accurate measurement and following directions.
KEY CONCEPTS
1. DNA, the genetic material of organisms, is composed of four kinds of nucleotides.
2. DNA is a molecule which consists of two strands with sugars and phosphates on the outside and nitrogen base pairs on the inside held together by weak hydrogen bonds.
Vocabulary Words
DNA (mitochondrial and genomic)
nucleotide
nitrogen base pairs
lysis
Context for Use
I use this lab on Day 2 of my DNA unit to reinforce the concept of DNA to 10th grade Biology students. My class sizes are normally around 24 students which lends itself for completion in one 50 minute class period. Equipment you may or may not have that is needed for this is a water bath and microcentrifuge tubes. The rest of the materials are accessible in most science labs and grocery stores. This could be used in many settings and situations. I even encourage students to try it at home with parents and siblings.
Description and Teaching Materials
Materials:(per student)
(1) 15 ml test tube with cap
(1) cup 8oz or larger
(1) eye dropper
Gatorade
25% soap solution
superglue
microcentrifuge tube
95% ethyl or 70% isopropyl alcohol
water bath access
clean glass stirring rod
fishing line
(1ml = 20 drops from the eye dropper)
Harvesting cells
1. Put about 10mls of gatorade in your mouth and swirl for about 30 seconds. While doing this scrape your teeth against your cheek to liberate as many cells as possible.
2. Spit the gatorade and cells back into your cup.
3. Put 2-3mls of the gatorade into your test tube and cap.
Lysis of cells/Release of DNA
4. Add 1ml of 25% the soap solution and recap tube.
5. GENTLY invert the tube 3-4 times. (DO NOT SHAKE)
6. Incubate the tube at 55 degrees C in the water bath for 1-5 minutes.
7. GENTLY invert the tube 3-4 times as soap lysis will open the cells up.
Precipitating the DNA
8. Hold the test tube at a 45 degree angle and slowly add 5 mls of ethyl alcohol down the side of the tube.
9. You may need to invert the tube gently to get the DNA to precipitate out efficiently.
10. At this point you should have 2 layers. (Cheek cells on the bottom and alcohol on the top.)
11. Hold the tube upright and the DNA should precipitate out.
DNA Collection
12. Add 0.5mls of ethyl alcohol to a microcetrifuge tube.
13. Place a clean glass stirring rod carefully remove the DNA by turning the rod in one direction.
14. Carefully remove the rod with the DNA and transfer it into the microcentrifuge tube containing ethyl alcohol.
15. Superglue the microcentrifuge tube closed and tie with fishing line to complete your DNA necklace.
16. Show your completed necklace to your instructor to receive your lab points!
(1) 15 ml test tube with cap
(1) cup 8oz or larger
(1) eye dropper
Gatorade
25% soap solution
superglue
microcentrifuge tube
95% ethyl or 70% isopropyl alcohol
water bath access
clean glass stirring rod
fishing line
(1ml = 20 drops from the eye dropper)
Harvesting cells
1. Put about 10mls of gatorade in your mouth and swirl for about 30 seconds. While doing this scrape your teeth against your cheek to liberate as many cells as possible.
2. Spit the gatorade and cells back into your cup.
3. Put 2-3mls of the gatorade into your test tube and cap.
Lysis of cells/Release of DNA
4. Add 1ml of 25% the soap solution and recap tube.
5. GENTLY invert the tube 3-4 times. (DO NOT SHAKE)
6. Incubate the tube at 55 degrees C in the water bath for 1-5 minutes.
7. GENTLY invert the tube 3-4 times as soap lysis will open the cells up.
Precipitating the DNA
8. Hold the test tube at a 45 degree angle and slowly add 5 mls of ethyl alcohol down the side of the tube.
9. You may need to invert the tube gently to get the DNA to precipitate out efficiently.
10. At this point you should have 2 layers. (Cheek cells on the bottom and alcohol on the top.)
11. Hold the tube upright and the DNA should precipitate out.
DNA Collection
12. Add 0.5mls of ethyl alcohol to a microcetrifuge tube.
13. Place a clean glass stirring rod carefully remove the DNA by turning the rod in one direction.
14. Carefully remove the rod with the DNA and transfer it into the microcentrifuge tube containing ethyl alcohol.
15. Superglue the microcentrifuge tube closed and tie with fishing line to complete your DNA necklace.
16. Show your completed necklace to your instructor to receive your lab points!
Teaching Notes and Tips
I mix the 25% dish soap solution up ahead of time which is enough for 100 students. I also buy a big can of gatorade mix and premix that up as well for students. You may also want to glue the tops on the microcentrifuge tubes on for the students. (Superglue is sometimes a potential problem)
Assessment
Students receive whatever lab points you wish to assign when they show you their completed DNA necklace!
Standards
(9-12.IV.D.1-Heredity)