In molecular biology, analysis of nucleic acids is commonly performed to determine the average concentrations of DNA or RNA present in a mixture, as well as their purity. Reactions that use nucleic acids often require particular amounts and purity for optimum performance. There are several methods to establish the concentration of a solution of nucleic acids, including spectrophotometric quantification and UV fluorescence in presence of a DNA dye. Nucleic acids absorb ultraviolet light in a specific pattern. In a spectrophotometer, a sample is exposed to ultraviolet light at 260nm, and a photo-detector measures the light that passes through the sample. The more light absorbed by the sample, the higher the nucleic acid concentration in the sample. An alternative way to assess DNA concentration is to use measure the fluorescence intensity of dyes that bind to nucleic acids and selectively fluoresce when bound (erg. Ethidium bromide). This method is useful for cases where concentration is too low to accurately asses with spectrophotometry and in cases where contaminants absorbing at 260nm make accurate quantitation by that method impossible. This book will prove beneficial to the students, teachers and researchers in the field of geography.
