DNA Extraction pg 55

Intro questions pg 55

• Where is DNA located in a Eukaryotic cell? (what is a Eukaryotic cell?)
• What would a scientist need to do in order to extract DNA from a eukaryotic cell?

DNA

Today you will extract DNA from some of your cells and learn more about DNA.

Extracting DNA from Your Cells

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. 

To extract DNA from your cells, you will need to separate the DNA from the other types of biological molecules in your cells.  You will be using the same basic steps that biologists 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

 

Getting Your Sample of Cells

Obtain a cup with sports drink.  You will need to get thousands of your cheek cells in the sports drink in order to extract enough DNA to see.  Therefore you should swish the sports drink around in your mouth vigorously for at least one minute. Then spit the drink back into the cup.

Step 1: Detergent

Get a clean test tube. Add a small amount of detergent to a test tube (about 0.25 mL).  Now carefully pour the drink containing your cheek cells into the test tube with detergent until the tube is half full. 

Step 2: Enzymes

Add a pinch of enzyme (meat tenderizer) to your test tube.  Place your thumb over the top of the tube; gently invert the tube five times to mix.  Place the tube in the test tube rack.  Let the mixture sit for at least 10 minutes.  While you are waiting, answer the questions on pg 55.

• Why am I adding detergent?
• Why am I adding enzymes? 
• The protease in meat tenderizer comes from plants, but animals also make proteases.  What is one reason why humans and other animals need to have protein-cutting enzymes?

Step 3: Alcohol

Using a pipette, slowly add cold rubbing alcohol into the test tube; let the alcohol run down the side of the test tube so it forms a layer on top of the soapy liquid. Add alcohol until you have about 2 cm of alcohol in the tube.  Alcohol is less dense than water, so it floats on top.  Do not mix or bump the test tube for 10 minutes.  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. 

• Why doesn’t the alcohol mix with the water?