Mechanical isolation—the incompatibility of sexual organs—is probably the simplest way to stop individuals from reproducing with each other. Whether it's the shape of the reproductive organs, the location, or differences in size that prohibit individuals from coupling, when the sexual organs don't fit together, mating is not likely to occur.
DNA extraction: A routine procedure used to isolate DNA from the nucleus of cells. DNA: Deoxyribonucleic acid (DNA) is a molecule that contains the instructions needed for an organism to develop and function. These instructions are stored as a code made up of four chemical bases: adenine (A), guanine (G), cytosine (C) and thymine (T).
Sorbitol-MacConkey (SMAC) agar was developed to take advantage of this characteristic by substituting the carbohydrate sorbitol for lactose in MacConkey agar and is the medium of choice for isolation of E. coli O157:H7 (4). Inoculate stool specimens onto SMAC and incubate 18-24 hours at 35-37C. Sorbitol-negative colonies will appear colorless ...