Extraction of DNA from Human Cheek Cells​ Activity      

Extraction of DNA from Human Cheek Cells​ Today you will extract DNA from your cheek cells.  This process is similar to what is done when any DNA-containing tissue is found at a crime scene.  ​ Cells from the lining of your mouth come loose easily, so you will be able to collect cells containing your DNA by swishing a liquid around in your mouth.   The cells from the lining of your mouth also come off whenever you chew food.  

Materials needed Water Dish Detergent Table salt Rubbing Alcohol

Extracting DNA from Your Cells To extract DNA from your cells, you will need to separate the DNA from the other types of biological molecules in your cells.   DNA is present in the cells of all living organisms.​ The process of extracting DNA from a cell is the first step for many laboratory procedures in biotechnology.​ The scientist must be able to separate DNA from the unwanted substances of the cell gently enough so that the DNA does not denature (break up).​

DNA is also coiled around proteins​ DNA is enclosed in a nuclear and a cell membrane made of phospholipids​ DNA is also coiled around proteins​ Both the phospholipid layer and the proteins must be removed to see DNA​

Nucleus with DNA Picture

Extracting DNA from your Cells You will be using the same basic steps that Forensic scientists use when they extract DNA (e.g. to clone DNA or to make a DNA fingerprint).  You will follow these 3 easy steps to extract the DNA:​   Detergent​ Enzymes (meat tenderizer)​   Alcohol

How to get your Sample In the first cup, mix a half glass of water (approximately 6 oz.) with 1 tablespoon of table salt. Label the cup 1. In the second cup, mix 3 tablespoons of water and 1 tablespoon of liquid dish soap. Label the cup 2. Take one teaspoon of the salt-water solution from the first cup and swirl it in your mouth for 30 seconds. After 30 seconds, spit the salt water and whatever contents are moving around in your mouth into a third empty cup. Label the cup 3

Step 1 Collect 1 teaspoon of the spit that is in cup number three, and transfer this to the fourth empty cup. Label the cup 4. Pour any extra spit down the drain. Add 1 teaspoon of the soap solution to the spit in cup number three, and mix by gently swirling the cup for one minute.

Step 2 After mixing, add three tablespoons of rubbing alcohol to the cup of spit and soap. Try to gently pour the alcohol down the side of the glass so that it floats up on top of the spit and soap without mixing. Wait about one minute, and you will see a cloud of bubbles hanging at the bottom of the layer of alcohol. Those bubbles are attached to your DNA!

Why did I add Alcohol? The cold alcohol reduces the solubility of DNA. When cold alcohol is poured on top of the solution, the DNA precipitates out into the alcohol layer, while the lipids and proteins stay in the solution. DNA molecules will clump together where the soapy water below meets the cold alcohol above, and you will be able to see these clumps of DNA as white strands. ​

Questions When you’re finished, answer these questions on a separate sheet of paper: 1.What does DNA stand for? 2.Where in your body can DNA be found? Research and write a paragraph about how forensic scientists use DNA in their jobs.