Molecular Biology
Assessment
Name ________________
Period _______
Questions should be answered and supported in each case. The explanation
is more important than your answer! Good luck!
Part I. An organic baker found canisters of unknown flour on seldom used
shelves in her pantry. They were not labeled, so she took them to a friend,
who just happened to be a molecular biologist. She needed to know if any
were genetically modified products, because she could NOT use them. The
biologist set up an experiment to extract DNA from the flours, then ran the
results through PCR and electrophoresis. The gel below shows the results.
Use the gel in answering the questions below.
Lanes
#1 tubulin (187bp)
#2 35s (162bp)
#3 Flour #1 + tubulin
#4 Flour #1 +35s
#5 Flour #2 + tubulin
#6 Flour #2 + 35s
#7 DNA ladder
The Gel
A. If we ran a protein such as actin (found in muscles) in Lane #1 instead of
tubulin, would this help us answer our question? Explain your response.
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B. What can you say about Flour #1 based on the results in Lane #4?
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C. What do the results in Lane #3 lead you to believe?
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D. Is unknown Flour #2 genetically modified? Use the results to support
your response.
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E. According to the results, can the baker use either of the flours? ______
Explain your response.
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F. Tell me again why the DNA ladder used was the best choice for the
experiment above.
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Part II. Drawing results on a gel
Background: You have just isolated DNA from different samples of beef,
chicken and lamb. We know that myosin (3500bp) forms a large part of the
muscles in mammals. The genes that regulate this protein can be engineered
to make the meat “meatier”. All test samples are subjected to PCR, and the
DNA then run on a gel. Your responsibility is to draw the results on the gel
in the appropriate lane. Think and you will be fine
Lanes
1 myosin(3500bp)
2 27s (1500bp)
3 beef +27s
4 beef+myosin
5 chicken+27s
6 chicken+myosin
7 lamb +27s
8 lamb +myosin
9 DNA ladder
Gel Results
a. A strong band appears at 3500bp in Lane 1.
b. A band appears at 1500bp on the gel in Lane 2.
c. No band appears in Lanes 5 and 6.
d. A strong band appears at 1500bp in Lane 3.
e. A strong band appears at 3400bp in Lane 4.
f. Circle the LONGEST DNA fragments on Lane 4.
g. Place a BOX around the shortest DNA fragments on Lane 3.
h. Would you expect to see a band on Lane 7? Why or why not?
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i. What reasonable results would you expect to see on Lane 8?
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j. Draw in appropriate end points for the DNA ladder used in this gel.
k. What reason might you propose for the lack of bands in lanes 5 and 6?
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Part III.
1. In order to identify GM organisms, the DNA must be examined. We used
a three step lab in order to do this. Tell me what happens basically at each
step of the process.
Step 1
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Step2:________________________________________________________
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Step 3:
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2. Taq polymerase and TE/RNAse are both enzymes used in this lab. What
would be the result if they switched places in the overall process( use TE
where I would normally use Taq)? What would this do to the final results?
4. If you had to choose a critical point in the GM Foods lab, where would it
be and why is it a critical point?