Polymerase Chain Reaction

Kary Mullis was awarded the Nobel Prize in 1993, for inventing the Polymerase Chain Reaction (PCR). This is a process, which assists in making billions of DNA copies, and has been a revolutionizing move in modern biology. This is a standard technique for anyone, who is studying DNA. This process helps in amplifying minute amounts of DNA samples for analysis and testing.

The physical properties are made use of a DNA in this PCR process. At temperatures of around 95oC, the two strands that constitute a DNA helix separate and unwind. These separate parts help in creating new DNA molecules. In a normal DNA strand, this is double-stranded, the bases of adenine (A) and guanine (G) pair with thymine (T) and cytosine(C) respectively. In the case of a single DNA strand, the complementary bases will attach themselves to the bases that are there on the single strands.

The PCR consists of five main components. They are-the DNA that has been gathered, and it has been purified. This is called the DNA template. There are small pieces of DNA that are single-stranded, and these are called primers. They attach to the complementary sequences on DNA molecules. There are four bases (A, T, G, C). These are to be added to primer, which will extend the complementary sequence, which will form new DNA. An enzyme called DNA Polymerase is needed, to extend the DNA molecule. Lastly, a buffer is needed that will create a favorable condition for the PCR.

All these components are placed in a device called a thermal cycler. The cycler carries out a process of heating and cooling, maintaining temperatures of 95oC, where the strands denature, 60oC, where the primer attaches to the strands and 72oC, where the primers are extended by the polymerase. This whole process is a cycle, which is run 25-35 times. Two copies of DNA template get produced after each cycle and the PCR products are multiplied through the cycles. This results in the formation of a billion copies of target sequence. DNA sample normally has more than copy, thus creating billions of the copies.