Directions: Please answer the following questions in complete sentences.

1. What problems might arise if the agarose wasn't dissolved completely or if there were air bubbles in the gel?
   
   
   
2. Why did you mix your DNA samples with a loading dye prior to loading the samples into the gel? Give 2 reasons.
   
   
   
3. What causes the DNA to travel through the gel?
   
   
   
4. Draw a sketch of what your gel would have looked like (after 5 minutes) if you reversed the positive and negative leads and placed the positive lead closest to the wells. Label the positive and negative leads, the wells, and the DNA.
   
   
   
   
   
   
5. Why did we get a single large band at the top of each gel when we loaded the DNA we had extracted from our cheek cells?
   
   
   
6. Why does the lane with 1 kb ladder have several bands?
   
   
   
   
7. Why do smaller DNA fragments travel further down the gel?
   
   
   
   
8. Study the gel below and answer the questions. Lanes are numbered from left to right.
   
   

Lane 1	1 KB ladder	Lane 5	50 ng/ul DNA
Lane 2	sample A	Lane 6	100 ng/ul DNA
Lane 3	sample B	Lane 7	200 ng/ul DNA
Lane 4	sample C

• Why is the band in lane 2 thicker and darker than the other bands?
  
  
  
• Why isn't there a band in lane 3?
  
  
  
  

9. Refer to lanes #5-7. Estimate the amount and concentration of DNA in the following lanes; 5 uL of DNA was mixed with the loading dye and added to each well:

• Lane 2: amount of DNA = _____ ng concentration of DNA = ______ ng/uL
  
  
• Lane 3: amount of DNA = _____ ng concentration of DNA = ______ ng/uL
  
  
• Lane 4: amount of DNA = _____ ng concentration of DNA = ______ ng/uL
  
  
  
  

Science Education Connection Department of Biochemistry The University of Arizona Tuesday, January 14, 1997 warder@u.arizona.edu http://biology.arizona.edu/sciconn/lessons/vuturo/ All contents copyright © 1997. All rights reserved.