Validation of Y-Chromosome STR (Y-STR) Multiplexes for Operational Use

We have developed the capability of typing 19 Y-STR loci in two multiplex systems, MPI and MPII, which include the loci DYS19, DYS385a, DYS385b, DYS388, DYS389I, DYS389II, DYS390, DYS391, DYS392, DYS393, DYS425, DYS434, DYS437, DYS438, DYS439, Y-GATA-A7.1, Y-GATA-A7.2, Y-GATA-H4, Y-GATA-C4. We have completed a full SWGDAM developmental validation of the MPI and MPII systems. The results show that MPI and MPII are suitable for casework use. The two multiplex systems are robust over a wide range of primer, magnesium and DNA polymerase concentrations and perform well under a variety of cycling conditions. Complete male haplotypes can be obtained with as little as 100-250 pg of template DNA. Although a limited number of female DNA artifacts are observed in mixed stains in which the male DNA comprises 1/300th of the total, the male profile is easily discernible. Slightly modified versions of MPI and MPII demonstrate a significant reduction in female artifacts. Thus, it may not be necessary to employ a differential extraction strategy to obtain a male haplotype (or haplotypes in the case of multiple male donors) in cases of sexual assault.

We have exemplified the potential utility of MPI and MPII in operational casework by their ability to dissect out the full 19 locus male haplotype in vaginal swabs taken up to 48 hours after intercourse. Partial profiles can be obtained 85 hours after intercourse. A judiciously chosen eleven-locus subset of our nineteen Y-STR loci is able to obtain a male donor profile 4 days after intercourse. This is accomplished by amplifying 300 ng of DNA from a non-differential extract of the cervico-vaginal swabs. This could result in a revolutionary approach to rape case analysis and establish Y-STR testing as a routine method in the crime laboratory.

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Jack Ballantyne
Department of Chemistry, CH 117
University of Central Florida
Orlando, FL 32816
Telephone: 407-823-0163
FAX: 407-823-2252
E-Mail: jballant@mail.ucf.edu