Successful deoxyribonuclease I (DNase I) phenotyping from a small piece of used sock.

The forensic application of the DNase I polymorphism for individualization of used socks is described. We devised a technique that combines a simple extraction method, including a partial purification step, using a Phenyl-Sepharose CL-4B column, isoelectric focusing and activity staining, for DNase I typing from socks. As a result, DNase I types were determined from socks kept at room temperature for a month or more in all of the samples tested. The DNase I types determined from socks exactly matched those determined from corresponding sweat and urine samples. By contrast, AB0 groupings could not be determined from these samples, using the conventional serological method. Therefore, we have shown that the DNase I polymorphism is the first genetic marker found to be well suited for individualization of used socks.