The Basics of DNA Analysis and Identification of Individuals

Test tube samples
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Based in the San Francisco Bay Area, Michael W. Sganga is a longtime forensic scientist who has provided expert testimony in a number of trials. Among Michael W. Sganga’s areas of focus is the use of DNA analysis in evaluating forensic evidence. 

DNA characterization is essentially an extension of forensic blood typing, which has been in use for many decades. Genetic variations are reflected in variations in proteins encoded by the DNA, which leads to individual differences within blood, including those that allow the identification of diseases such as phenylketonuria and cystic fibrosis.

Instead of typing the proteins coded for by DNA, DNA analysis involves a typing of the actual DNA. With an aim of personal identification, molecular genetics allows parts of the DNA that distinguish individuals to be analyzed. 

One fundamental technique of DNA analysis is "Southern blot,” which involves the separation of DNA sample fragments through use of an electrical field. Those fragments of interest are further analyzed by using a labeled probe, or short single-stranded DNA segment, that contains a radioactive atom. The end result is a more flexible way of identifying people based on DNA that does not require a blood sample.