Michael A. Marino, Lois A. Tully, Robert J. Steighner and Phillip Belgrader
Armed Forces DNA Identification Laboratory, Armed Forces Institute of Pathology, Rockville, MD 20850

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Forensic DNA identification of skeletal remains relies mainly on the sequence information obtained from mitochondrial DNA. Presently used sequencing instrumentation offers the advantage of simultaneous multiple sample analyses, but is labor and time intensive and does not lend itself to total automation. Capillary electrophoresis (CE) offers an attractive alternative to traditional slab gel sequencing of fluorescently labeled DNA fragments. Via automation, fresh polymer sieving agents are loaded into a capillary prior to each sample analysis. Also, unlike traditional gel electrophoresis, samples are introduced into the matrix by electrokinetic injection. The most notable difference between the cast gel and capillary formats is analysis time.

The capillary has a high surface volume which provides excellent heat dissapation, allowing higher applied voltages and therefore shorter run times. For this study, applied voltages of greater than 250 volts per centimeter were used to sequence the hypervariable region of human mitochondrial DNA. The CE analysis used a derivitized thin-walled fused silica capillary with an interior diameter of 100 µm and total length of 47 cm. The system detector is on-column, increasing the sensitivity and resulting in the need for less concentrated samples. Samples were sequenced at a rate of 250 bases per hour and results were comparable to those obtained by slab gels.