Ever wonder what a picture like the one below means?  Have you seen it on TV before (like on C.S.I. or another law/crime show)?

Well, now you will know!  Basically, the little bands you see up there are small pieces of DNA.  Each column is a different person's DNA that has been cut up by restriction enzymes.  Once scientists have run the small pieces of DNA out on the gel (what you see above), they can compare and match people's DNA!

Below is a link to a cool video (an interactive virtual lab) that tells you how to do your own DNA electrophoresis experiment.  We will do something like this to solve the Shamari Davis murder mystery...

DNA Gel Electrophoresis 

Please use the video to answer the questions.  It might be helpful to write the questions down before you start the video...

Questions:

1.  Is there a way to sort and measure DNA strands?  What is it called?

2.  When you do DNA electrophoresis, what are you sorting the strands by?  (Length, color, or type of gene?)

3.  What is a "gel"?

4.  When you are using a gel, where does the DNA go?

5.  Why do we use electricity?  In other words, why is it called electrophoresis?

6.  Which strands of DNA move further, shorter strands or longer strands?  Why? 

7.  What are "bands" on the gel?

8.  What are the 5 steps of DNA electrophoresis?

9.  What materials/equipment do you need for Step 1?

10.  In Step 1, what do you use to make the gel?  In other words, what are the ingredients?

11.  What is the "buffer"?

12.  What happens when we heat the agarose in the microwave?

13.  Why do we use the "comb"?

14.  What happens to the melted gel after it has sat out for a while?

15.  In Step 3, what is the point of the "loading buffer"?

16.  In Step 3, what is the point of the "DNA size standard"?  In the picture above (on this page), where is the DNA size standard located?

17.  In the picture above (on this page), are any two samples of DNA matching?  Which ones?

Click on this link to go back to learning how to extract DNA.

Click on this link to see how we can use this information in an actual criminal investigation.