Katherine A. Micka, Ann M. Lins, Jeff Bacher, Jennifer Taylor, and James W. Schumm
Promega Corporation, Madison, WI

× Ø × Ø × Ø × Ø × Ø × Ø × Ø × Ø × Ø × Ø × Ø × Ø × Ø × Ø × Ø

Comparison of a variety of primers for amplification of the locus D7S820 has displayed variable results. When selected samples were amplified with the primers described by the Cooperative Human Linkage Center (CHLC) they appeared as homozygotes with a n-4 band. Amplification of these same samples using primers described at the Sixth International Symposium on Human Identification in the poster, "Evaluation of a New STR Multiplex (D5S818, D13S317, D7S820 for Forensic Applications" by Fourney, R.M., et al., produced a more enigmatic result, an apparent heterozygote with one allele displayed more strongly than the other.

By designing our own primers to amplify a different portion of the D7S820 locus, we were able to eliminate this ambiguity. In fact, the GenePrint^tm D7S820 primers clearly demonstrate that these samples are true heterozygotes. We have selected the newly modified D7S820 primers for inclusion within the GenePrint™ PowerPlex™ System.

This study clearly demonstrates the importance of proper design of primer sequences and the necessity to test a large sample population for diversity. In this particular case, the African-American population shows the allele ambiguity most frequently.