Polymerase Chain Reaction (PCR)
Polymerase Chain Reaction (PCR) is also known as Molecular Photocopying is used to make many copies of a small segments of DNA. It is a relatively inexpensive and fast method. Sometime, the quantity of DNA requires is not enough for doing a test, therefore it is necessary to duplicate more DNA to increase the accuracy and reliability of the result.
A particularly useful feature of PCR is that it allows the amplification process to be limited to specifically targeted segments of the DNA mixture such as the Y chromosome markers used in genealogical testing.
Your DNA can be simply taken from the cheek cells and send to the laboratory for testing. They will use detergent to cause the cells to burst open and release the DNA before washing it with a phosphate containing buffer solution to dilute cellular debris. The sample is now ready for the PCR to amplify.
PCR works because of DNA polymerase enzyme that can synthesize a complementary strand to a targeted segment of DNA in a test tube mixture of the 4 DNA bases. The mixture must also contain 2 DNA fragments, each about 20 bases long, called the primers. You will need to know the DNA sequence around the region you want to amplify before doing PCR. The primers can be purchased from commercial suppliers or can be constructed in the lab.
The mixture is first heated to denature or separate the sides of the double stranged DNA and then cooled to allow the primers to find and bind to their complementary sequences on the separated strands and the polymerase to extend the primers into new complementary strands. Repeated heating and cooling cycles multiply the target DNA exponentially, since each new double strand separates to become 2 templates for further synthesis. In about an hour, 20 PCR cycles can amplify the target by a million fold. In 32 cycles at 100% efficiency, 1.07 billion copies of targeted DNA region are created.
The entire cycle can be completed in just an hour with the use of thermocycler, programmed to change the temperature of the mixture every minutes so that the double strand will be denature and synthesis continously.
PCR is able to detect bacteria and virus DNA. Viruses such as HIV in very small quantity can be amplify in large quantity to read the DNA.
A particularly useful feature of PCR is that it allows the amplification process to be limited to specifically targeted segments of the DNA mixture such as the Y chromosome markers used in genealogical testing.
Your DNA can be simply taken from the cheek cells and send to the laboratory for testing. They will use detergent to cause the cells to burst open and release the DNA before washing it with a phosphate containing buffer solution to dilute cellular debris. The sample is now ready for the PCR to amplify.
PCR works because of DNA polymerase enzyme that can synthesize a complementary strand to a targeted segment of DNA in a test tube mixture of the 4 DNA bases. The mixture must also contain 2 DNA fragments, each about 20 bases long, called the primers. You will need to know the DNA sequence around the region you want to amplify before doing PCR. The primers can be purchased from commercial suppliers or can be constructed in the lab.
The mixture is first heated to denature or separate the sides of the double stranged DNA and then cooled to allow the primers to find and bind to their complementary sequences on the separated strands and the polymerase to extend the primers into new complementary strands. Repeated heating and cooling cycles multiply the target DNA exponentially, since each new double strand separates to become 2 templates for further synthesis. In about an hour, 20 PCR cycles can amplify the target by a million fold. In 32 cycles at 100% efficiency, 1.07 billion copies of targeted DNA region are created.
The entire cycle can be completed in just an hour with the use of thermocycler, programmed to change the temperature of the mixture every minutes so that the double strand will be denature and synthesis continously.
PCR is able to detect bacteria and virus DNA. Viruses such as HIV in very small quantity can be amplify in large quantity to read the DNA.
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