The polymerase chain reaction, or PCR, has revolutionized genetic research. Virtually all genetic research, from creating new drugs to studying endangered species, requires the duplication of DNA. Until the mid-1980s, scientists copied DNA fragments by inserting them into bacteria, and cloning the bacteria-an expensive, time-consuming process. Now, using PCR, they can easily make billions of copies in a few hours.
In the laboratory, there are several steps that lead to the preparation of a sample so that the PCR technique may be used. These include isolating the genetic material or DNA and placing it in a new test tube; adding the necessary ingredients to the new test tube (e.g., primers, DNA polymerase, or nucleotides); and placing the test tube into the PCR machine.
The uniqueness of PCR is that once you have copied some DNA, you can repeat the process and copy the copies. To do this, you simply heat and cool the solution, over and over. Each time you run the cycle, you double the product. After 10 such doublings, you will have over a thousand times the original amount of DNA. Ten additional cycles make a thousand of each of the original DNA strands, for over a million strands total. Thirty cycles yield a billion copies of the original DNA strand, in only two and a half hours.
Use the PCR Simulation to see this process. Then take time and reflect on the natural process that PCR mimics and why you think it has been such a revolutionary technique for molecular biologists.
Click here for a copy of the directions for using the PCR Simulation that you can print and follow. These directions are also found in the simulation.