This is from the scientist who performs the tests.
Now that we have the DNA, we have to make copies of the region that we’re interested in. DNA extraction is not limited to one type of DNA. When you extract the DNA from a fecal sample, you are getting DNA from the microbes. But you may also be getting DNA from the plants the person is eating, or from other cells that are in the fecal material. We don’t care about that DNA, so we have to separate it out. We do that by making lots of copies of the microbial DNA and throwing away all of the other DNA.
We make copies of the microbial DNA using polymerase chain reaction.
Polymerase chain reaction, or PCR, mimics how DNA is copied in nature.
PCR is the usual technique.