PCR has many uses in a biological or biochemical setting. Because DNA is unique for every living thing, experimenters can often extract only small amounts of the DNA they are interested in from a specimen. These amounts are usually too little to be useful, and so a scientist will use PCR to make enough copies to start experimenting with. For this reason, it is one of the most common techniques used in genetics labs around the world, making it useful in experiments on many things, including gene therapy, infectious diseases, and even forensics.