Apple Molecular Biology
cDNA Cloning & Isolating plasmid DNA from bacteria
Directions
1. Go to the Apple Genomics website at www.four-h.purdue.edu/apple_genomics
2. Click on the link Apple Molecular Biology.
3. Click on the link Cloning.
4. After reading the introduction click on the third and fourth animation to learn
more about cloning.
5. Then complete the review questions on this worksheet using what you learned
from the reading and animation.
Cloning and Replication
A plasmid is a small circular strand of chromosome, and is found in bacteria. Generally, they include some region of
DNA that confers antibiotic resistance so any organism containing the plasmid can be selected on a growth media
containing the appropriate antibiotic. Scientists have learned how to modify plasmids to function as molecular tools.
The fourth animation explains how complementary DNA or cDNA is created by inserting the cDNA into plasmid
vectors.
Bacterial colonies are selected and moved into liquid growth media for another period to increase the numbers of that
specific colony. The DNA can be extracted from these millions of cells and the foreign DNA can be removed from the
plasmid. The fifth animation in the series describes in detail using visual references how the bacterial colonies are
selected for and how DNA extraction occurs.
Cloning DNA using bacterial vectors allows scientists to preserve specific fragments of DNA in a cell. The bacteria can
be frozen and used later to transfer the foreign DNA into an appropriate host. Transformed plants or animals can then
be studied to determine the effect of the new gene.
Key Terms:
Define the following key terms that were discussed in the reading and or the animation.
1. Complimentary DNA
2. Reverse Transcriptase
3. Transformation
4. Centrifuge
5. Vector
What Did You Learn?
Answer the following questions using complete sentences.
6. Why is the antibiotic resistance gene in a plasmid important?
7. Draw and Describe. How are genes spliced into bacterial plasmids? Draw and label a
diagram to explain this process.
8. Explain how DNA is isolated from bacterial recombinant plasmids?
9. Explain why it is necessary to add alcohol to a solution during the process of extracting
DNA from living cells?
10. Describe how scientists can use transformed plants or animals to study the effects of
specific genes.