The Importance of PCRs

A common technique used in the research lab is the PCR (Polymerase Chain Reaction). It is used to amplify trace amounts of DNA within a liquid. These amplified segments of DNA can then be compared to DNA from a known source, thus letting the researcher know if they have amplified the right gene, or can tell them the source of a certain segment of DNA. PCRs are run in small tubes, and a small portion of the amplified sample can be mixed with blue dye and run on a gel (see previous post on  Gel Electrophoresis) for comparison. Often, scientists use a ladder that serves as a comparison point in terms of sizes. The ladder has known sizes of DNA bands spread across a range on the gel.



The picture above shows one of my sample PCRs. In this one, I used different concentrations of plasmid, and got slightly different results (this will be discussed later). From the picture, the DNA ladder can be seen on the left. The very slight band of DNA matching up with the three PCRs after that corresponds to the size of the fragment.