SNP typing of low template DNA.
Børsting, C.
Mogensen, H.S., Morling, N.

Section of Forensic Genetics, Department of Forensic Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark

Low template DNA (LtDNA) typing is complicated by the occurrence of stochastic phenomena that results in skewed amplification of alleles and loci. The result is frequent heterozygote imbalances and, in the extreme situation, allelic or locus drop-out. The number of drop-outs may be reduced by increasing the sensitivity of the typing assays and different methods have been used for LtDNA typing of STRs. However, the sensitizing STR typing protocols have two major drawbacks: 1) the signal from stutters increases, and 2) the number of drop-in alleles increases dramatically from approximately zero with the standard protocols to 1-3% of the approved alleles with the sensitized protocols.
Here, we present a sensitized SNP typing protocol that increases the signal strength without affecting the noise or the heterozygote balance. The protocol allows SNP typing of LtDNA with high accuracy and it improves the typing success of challenging crime case samples.