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Capillary Electrophoresis STR Analysis: Comparison of Gel- Based Systems

NCJ Number
Date Published
January 1998
20 pages
This study examined the ability of capillary electrophoresis (CE) to separate and type PCR (polymerase chain reaction) amplified DNA fragments from several STRs (short tandem repeats) loci currently in use for forensic individualization.
The samples analyzed by CE had previously been run and typed in a variety of gel-based systems in several different laboratories. The results show that capillary electrophoresis yields the same results obtained by those gel-based technologies when allelic ladders are used to standardize the technique. Results obtained from either technique are comparable, so that databases constructed using one technology can be searched or compared directly to another. Proficiency tests and other experimentally derived data can also be easily compared. CE is a new approach in the analysis of DNA fragments, particularly STRs. This study has shown that CE is capable of distinguishing alleles with single base pair resolution and that within the CE system, base pair sizing is repeatable. The average base pair range determined for any allele within a locus is considerably less than a base pair. Consequently, although base-line resolution was not achieved for single base pair variants, the resolution was sufficient to designate alleles accurately on the basis of base pair size that are not overlapping. As demonstrated, CE allows the analyst to identify the STRs examined and offers some advantages over gel-based technologies. The conventional gel-based technologies require the preparation, loading, and subsequent analysis of gels. The space and time associated with these processes are considerable. The CE unit is relatively small and requires a minimal amount of supporting equipment and space. The capillary columns are easy to replace, and samples are placed within an autosampler for automatic loading. Samples that require rerunning can be automatically reinjected and analyzed by the instrument without the need to remake a gel and reload the samples. 15 references, 3 tables, and 2 figures

Date Published: January 1, 1998