Polymerase Chain Reaction (PCR) Testing Methodology
In the laboratory field a method called Polymerase Chain Reaction (PCR) is used for
analytical purposes such as amplifying DNA. Kary Mullis who was awarded the
Nobel Prize in Chemistry for developing this method developed it in 1983. It is now
a commonly used technique for research purposes in labs around the world. This
method is also used for DNA cloning for sequencing, functional analysis of genes,
the diagnosis of hereditary diseases, the identification of genetic fingerprints (used
in forensic sciences and paternity testing), and the detection and diagnosis of
infectious diseases.
How it works
The PCR technique amplifies one or many copies of a piece of DNA to generate
thousands to millions of copies of a particular DNA sequence. This method relies on
thermal cycling, which consists of
cycles of repeated heating and
cooling of the reaction for DNA
melting and enzymatic replication
of the DNA. The PCR method uses
an enzyme as a catalyst for the
chain reaction. A commonly used
enzyme is a Taq polymerase. The
DNA polymerase assembles a
new DNA strand from
nucleotides, which are considered
the DNA building blocks. The
method can then use a single
stranded DNA as a template to
initiate DNA synthesis.
Why it is important
PCR permits for the early diagnosis of malignant diseases such as leukemia and
lymphomas. The PCR method is currently the highest developed method in cancer
research. PCR assays can be performed directly on genomic DNA samples to detect
malignant cells at a sensitivity that is at least 10,000-fold higher than that of other
methods. PCR also permits identification of non-cultivatable or slow-growing
microorganisms such as mycobacteria, anaerobic bacteria, or viruses from tissue
culture assays. The high sensitivity of PCR allows for virus detection soon after
infection and even before the onset of disease. The ability for early detection can
give physicians a significant lead in treatment.