NUCLEIC ACID ANALYSIS
Analysis of the DNA or RNA of microorganisms is the basis of newer taxonomic studies and increasingly applied to diagnostic and epidemiologic work. It is also possible to use cloned or synthesized nucleic acid probes to detect genes or smaller nucleotide sequences specific for a variety of bacterial, viral, and other infectious agents. As with antigen – antibody reac- tions, a variety of methods have been developed for analysis of nucleic acids. Those relevant to the study of infectious diseases are briefly summarized below. The student is referred to textbooks of molecular biology for more complete coverage. DNA is a hardy molecule that will withstand fairly harsh chemical treatment. RNA is more fragile, primarily because it is readily digested by the RNAse enzymes commonly found in biologic systems. The extrac- tion process for bacteria and fungi involves breaking open the cells, precipitating the protein, and extracting the nucleic acid with ethanol. Viral procedures are similar except that much of the separation and concentration may be accomplished by ultracentrifugation.