Polymerase Chain Reaction and Genetic
One of the most significant contributions to the field of genetics is the invention of the Polymerase Chain reaction (PCR). With this technique, billions of copies of DNA can be amplified in a short period of time. So how does this experiment actually work? There are essential components that this experiment needs: chromosomal DNA, deoxynucleotides, Taq polymerase, forward primers and reverse primers. There are three steps in the PCR process, which include the denaturing step, the annealing step and extension step. In the denaturing step, the target DNA sequence is heated up to around 94 C. The heat breaks the hydrogen bond and two single DNA strands forms. After the denaturing process is completed, the temperature is then cooled to about 65C, and the annealing step occurs. During the annealing step, primers anneal to the base pair with the chromosomal DNA. Because the replication of DNA is from the 5’ to 3’ direction, the use of the primer is needed for the polymerase to start synthesis. After the annealing the step is completed, the elongation process can begin. The Taq polymerase is used because it is not temperature sensitive, and it is used to synthesize the strands. After about 30 cycles of this process, we end up with about a billion copies of the target DNA.
Now that we understand how the process works, we can now understand what PCR is used for. PCR is especially useful in the field of genetics. One common use for PCR is for paternity tests. Between different humans there are variable polymorphic regions. If we test one person at a specific location (loci) and test another person at the same loci they will have different genes. Therefore, if we compare loci of different individuals and compare it with a child’s DNA we can gain insight to who the parents are. Those individuals that have similar gene sequences with the child are most likely the parents. PCR is used to amplify DNA so that it is possible to analyze these polymorphic regions. There are other benefits to PCR in the field of genetics. PCR is also used to test individuals for predisposition of diseases. PCR can be used to detect small variations of DNA sequences. Therefore by comparing an individuals DNA, to an infected person’s DNA we can predict the odds in which the individual we also get the disease. If an individual has a similar variation of an infected person, we know that they are predisposed for that disease. A disease that can be tested by this method would be cystic fibrosis. Scientists are also trying to apply this method to cancer as well as heart diseases. PCR is a powerful technique that has revolutionized the field of genetics.