With the discovery of DNA, its structure and enzymes which cut and reattach DNA has come the biotechnology revolution. The techniques of the molecular biologist have proved themselves to be powerful tools to answer all kinds of biological questions, including questions about the evolution of species and biological diversity. To investigate whether the populations of cacti growing around Globe, Arizona, are a valid variety (a geographical race) of the species E. triglochidiatus, it is possible to study the DNA of individual cacti within each population, and then to compare the DNA of each population to the other. By looking at the degree of similarity and difference between populations, it can be determined if the populations are sharing their genes by breeding with one another. If the populations are geographically and/or reproductively isolated, then the populations will likely show a greater degree of genetic difference than those populations which are actively interbreeding.

In order to analyze the cacti at the genetic level, we will have to do three things:

(1) Isolate and purify the DNA from the cells of the plant tissue.

(2) Amplify, using Polymerase Chain Reaction, only small, randomly scattered regions of the extremely large genome in order to see similarities and differences in the sequence of the DNA more easily (a way to perform a "DNA fingerprint").

(3) Analyze these amplified regions of the DNA through the use of gel electrophoresis.