Note on PCR- Techniques | Explanations PCR

 PCR - polymerase chain reaction 

What is PCR (polymerase chain reaction)?

PCR is a technique used in the lab to make millions of copies of a particular section of DNA. It was first developed in the 1980s. Polymerase chain reaction (PCR) is a method widely used to rapidly make millions to billions of copies of a specific DNA sample, allowing scientists to take a very small sample of DNA and amplify it to a large enough amount to study in detail. PCR was invented in 1984 by the American biochemist Kary Mullis at Cetus Corporation.

What is PCR?

                 Polymerase chain reaction ( PCR)                     is a technique used to "amplify"                       small segments of DNA. 

• The polymerase chain reaction (PCR) was originally developed in 1983 by the American biochemist Kary Mullis. He was awarded the Nobel Prize in Chemistry in 1993 for his pioneering work.

PCR is a three-step process that is carried out in repeated cycles. The initial step is the denaturation, or separation, of the two strands of the DNA molecule. This is accomplished by heating the starting material to temperatures of about 95 °C (203 °F). Each strand is a template on which a new strand is built. In the second step the temperature is reduced to about 55 °C (131 °F) so that the primers can anneal to the template. In the third step the temperature is raised to about 72 °C (162 °F), and the DNA polymerase begins adding nucleotides onto the ends of the annealed primers. At the end of the cycle, which lasts about five minutes, the temperature is raised and the process begins again. The number of copies doubles after each cycle. Usually 25 to 30 cycles produce a sufficient amount of DNA.

• PCR is used in molecular biology to make many copies of (amplify) small sections of  DNA or GENEs.
• Using PCR it is possible to generate thousands to millions of copies of a particular section of DNA from a very small amount of DNA.
• PCR is a common tool used in medical and biological research labs. It is used in the early stages of processing DNA for sequencing for detecting the presence or absence of a gene to help during infection, and when generating forensic DNA profiles from tiny samples of DNA.

How does PCR work?

• The principles behind every PCR, whatever the sample of DNA, are the same.  the DNA template to be copied primers, short stretches of DNA that initiate the PCR reaction, designed to bind to either side of the section of DNA you want to. 
• • buffer to ensure the right conditions for the reaction.
• PCR involves a process of heating and cooling called thermal cycling which is carried out by machine.
• There are three main stages:
1. Denaturing – when the double-stranded template DNA is heated to separate it into two single strands.
2. Annealing – when the temperature is lowered to enable the DNA primers to attach to the template DNA.
3. Extending – when the temperature is raised and the new strand of DNA is made by the Taq polymerase enzyme  

               

           

                Applications Of PCR:

               1. Selective DNA isolation

               2. In Research and in forensic application 

               

               3. Amplification and quantification of DNA

               4. Medicals and diagnostic applications 

               5.Infectious disease applications -

PCR allows for rapid and highly specific diagnosis of infectious diseases, including those caused by bacteria or viruses.