Gene Dog Blog

We live in the era of technology. Technology is used in field whether it is related to biology, physics, computers, chemistry or any other. Today, we will look at supremely technical phenomena in the field of bio technology called Polymerase Chain Reaction.

What is PCR?

PCR is a technology based machine that is used in the field of biotechnology. PCR is used for the amplification of DNA- producing accurate copies of single-stranded sequence. It is used to amplify a sample of DNA when there isn’t enough to analyze (sample of DNA from a crime scene, archeological samples).

Functionality and Importance of PCR

It is a very important and helpful tool in the field of molecular biology, genetics, forensic, evolution, paternity testing and mutation. During the working of PCR a reaction takes place commonly known as PCR reaction. Reaction requires several components to function i.e., template DNA, oligonucleotide primers, deoxynucleotide triphosphates (dNTPs), magnesium chloride, key ingredient, DNA polymerase and taq polymerase that is obtained from the thermostable bacterium Thermus aquaticus most commonly used to drive the replication process. Primer is also a very important component of the reaction. Primers are short sequences of nucleotides designed to bind either side of the region of interest on the DNA molecule to be analyzed. Fragment of a DNA is double stranded.

Steps of PCR

PCR reaction consists of three main steps that are denaturation, annealing and extension.

1. Denaturation: One to several minutes at 94-96 C° during which the DNA denatured into single strands.
2. Annealing: At 50-65 C ° during which the primers hybridize or “anneal” (by way of hydrogen bonds) to their complementary sequences on either side of the target sequence.
3. Extention : For fragments up to 3 kb primer extension is normally carried out  at 72 C ° during which the polymerase binds and extends a complementary DNA strand from each primer and add approximately 60 bases per second at 72C°.

During the whole process PCR machine works like a copying machine. Each cycle result in a doubling of the starting template material. In a standard 30-cycle reaction a single template molecule can produce over 250 million copies.

Applications and General Use of PCR:

• Method of identifying a gene of interest, or to test for disease.
• PCR detect and identify bacteria and viruses causing infections such as tuberculosis, HIV, and many others.
• Once primer’s designed for the DNA of a specific organism, using PCR to detect the presence or absence of a pathogen in a patient’s blood or tissues simple experiment.
• Used in genetic testing to determine whether patients carry a genetic mutation that could be passed on to their children (e.g. the mutation)
• Used to detect evolutionary relationships on ancient samples.
• Genes from various related organisms amplified, sequenced and then analyzed for similarities/differences.
• If two organisms have very similar genetic sequences, they are most likely closely related.

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About the author: Tarhub Asghar is a biotechnologist who has been in the field for more than two years. One day she hopes to get a PhD in the discipline. Tarhub’s other interests include home buying and Hosted Exchange.

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