WWLPT

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Let’s Do the PCR Time Warp:
Teacher Dialectic Demonstration

Objectives

Materials

Procedure

Internet Resources

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Background

One important technology of genetic engineering has been the development of methods for producing copies of DNA or DNA amplification.  In the 1970’s the procedure required the cumbersome insertion of a pre-cut DNA fragment into a bacterial plasmid and the transformation and growth of a bacteria cell with this transgenic plasmid.  In the 1983 Kary Mullis conceived and developed an ingenious method for amplifying fragments of DNA called polymerase chain reaction (PCR).

The following demonstration was produced for those teachers who do not have access to a PCR machine and do not have enough time to complete a manual PCR (the students could get quite bored with this too).  In general, the following activity is a more enjoyable and interactive alternative to teaching the concepts of PCR amplification of DNA. 

1. Given an initial parent strand of DNA having a particular nucleotide sequence students should be able to outline the detailed steps by which a segment of one of the strands is amplified into millions of DNA strands when using the PCR method.
    

Materials

Fake DNA sample
Fake PCR Chemicals (dNTP’s, Primers, and DNA Polymerase, Buffer)
Eppendorf tubes for DNA samples
Styrofoam or similar floatation device for DNA samples
3 Large Beakers
3 Thermometers
3 Hot Water Baths
Beaker of Ice

Demonstration Procedure

Write the sequence for a double strand of DNA on the chalkboard and include a key for dNTP’s, forward and reverse primers, DNA polymerase, and buffer.

5’ ATCGCTTACGTCAACT 3’        original strand
3’ TAGCGAATGCAGTTGA 5’        original strand

Then, complete the following steps.  In each, you will find information on the PCR Demonstration, the Discussion that you should have with your students, and the information that you should then have on the Chalkboard when your students have figured out what is going on in the demonstration.

1. Denature DNA
2. Anneal Primers
3. Extend Nucleotides
4. Second Cycle
5. Third Cycle & Beyond

Reference

Kary B. Mullis (1990)  The Unusual Origin of the Polymerase Chain Reaction, Scientific Amerian, April, pages 56-65.

 Internet Resources

 | Background | Objectives | Materials | Procedure |
| File Format for Printing |