DNA Cheek Cell Extraction

Name ______Period ______Date ______DNA Cheek Cell Extraction

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.

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: Define in your own words DNA: ______nucleotide: ______nitrogen base pairs: A in one strand always pairs with _____ in the other strand. C in one strand always pairs with _____ in the other strand. lysis: ______

Materials: clean glass stirring rod Per group Teacher’s Materials (1) 15 ml test tube 25% soap solution (1) Dixie cup 95% ethyl or 70% isopropyl alcohol (1) dropper

Procedure: Harvesting cells 1. Scrape the inside of your cheeks with your teeth DO NOT SWALLOW. 2. Put about 5mls of salt water in your mouth and swirl for about 30 seconds. 3. Spit the salt water and cells back into your cup. 4. Put 5 mls of the salt water into your test tub.

Lysis of cells/Release of DNA 5. Add 5ml of 25% the soap solution. 6. GENTLY invert the tube 3-4 times or swirl it on its side. (DO NOT SHAKE)

Precipitating the DNA 7. Hold the test tube at a 45 degree angle and slowly add 5 mls of ethyl alcohol down the side of the tube. 8. Place your thumb over the top of the test tube and invert the tube gently (turn upside down) to get the DNA to precipitate out efficiently. 9. At this point you should have 2 layers. (Cheek cells on the bottom and alcohol on the top.) 10. Hold the tube upright and the DNA should precipitate out.

DNA Collection 11. Add 0.5mls of ethyl alcohol to a test tube. 12. Place a clean glass stirring rod carefully remove the DNA by turning the rod in one direction to collect the DNA around the stirring rod. Discussion Questions

1. What are the building blocks of DNA? ______Draw and label it below.

2. What is the function of DNA from day to day? 3. Describe how long strands of double-helical DNA fit into the nucleus of a single cheek cell.

4. What was the purpose of using the cell lysis solution?

5. Why does the DNA become visible once the alcohol is added?

6. If DNA is so thin, how is it that we are able to see it during this simple lab exercise?

For the two sections of DNA shown to the right: Yes or No Is the arrangement of the sugar and phosphate groups the same in both sections of DNA? Do both sections of DNA contain the same four bases (A, C, G, and T)? Are the base-pairing rules the same in both sections of DNA? Is the sequence of nucleotides the same in both sections of DNA?

8. What is the only difference between these two sections of DNA? ______

9. The drawing below shows the short segment of DNA from the previous question, after the two strands of the DNA molecule have been separated in preparation for replication. Your job is to play the role of DNA polymerase and create the new matching strands of DNA to make two pieces of double-stranded DNA in the drawing below.

Old Strand New Strand New Strand Old Strand

10. Look at both of the double-stranded pieces of DNA you have created. Are there any differences between these two pieces of DNA?

11. Are these new double-stranded pieces of DNA the same as or different from the original piece of DNA from question # 7?

12. Why is it important that both copies of the DNA molecule have the exact same sequence of nucleotides as the original DNA molecule?

13. Explain why DNA replication is needed before a cell divides into two daughter cells.