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PCR is a laboratory method used for making a very large number of copies of short sections of from a very small sample of genetic material. This process is called "amplifying" the DNA and it enables specific of interest to be detected or measured.
DNA is made up of repeating sequences of four bases – adenine, thymine, guanine, and cytosine. These sequences form two strands that are bound together in a double helix structure by hydrogen bonds (like a spiral staircase). Each half of the helix is a complement of the other. In humans, it is the difference in the sequence of these bases on each strand of DNA that leads to the uniqueness of each person's genetic makeup. The arrangement of the bases in each gene is used to produce RNA, which in turn produces a . There are about 25, 000 genes in a human genome, and expression of these genes leads to the production of a large number of proteins that make up our bodies. The DNA of other organisms such as and is also composed of thousands of different genes that code for their proteins.
How is the method performed?
PCR is carried out in several steps or "cycles" in an instrument called a thermocycler. This instrument increases and decreases the temperature of the specimen at defined intervals during the procedure.