Abstract
Obtaining genetic profiles from samples containing minimal amounts of DNA can be difficult.
In forensic science, the vast majority of genetic profiles are generated using commercial
kits that have been optimized for the amplification of a specific range of DNA concentrations.
DNA extracted from many forensic samples falls below the kit manufacturers’ specified
concentrations either because there is not enough total DNA in the extract or the
extract is so dilute that not enough volume of the extract can be added to the PCR.
In order to develop a method to maximize SGM Plus® and Identifiler® profiling success from samples with sub-optimal quantities of DNA, thermocycle numbers
and/or the amount of PCR product injected during capillary electrophoresis (termed
Enhancement) of PCR products were increased. Increasing the number of thermocycles
from 28 to 30 and/or two phases of Enhancement of both 28 and 30 thermocycle PCR products
resulted in an increased number of scorable peaks. As expected with low template amounts
of DNA, many of the samples showed allelic drop-out, heterozygote imbalances and sporadic,
large stutter peaks. Enhancement decreased the amount of allelic drop-out observed
and did not affect stutter peak or heterozygous peak height ratios. Although the PCR
reactions from these samples should always be replicated before a reportable consensus
profile is reached, Phase 1 and 2 Enhancement can maximize the profiling success from
each reaction. Finally, a flexible, staged approach using 28 or 30 thermocycle PCR
in combination with the Enhancement techniques described here is proposed for processing
samples with sub-optimal quantities of DNA.
Keywords
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Article info
Publication history
Published online: February 02, 2009
Accepted:
December 13,
2008
Received in revised form:
October 13,
2008
Received:
July 18,
2008
Identification
Copyright
© 2008 Elsevier Ireland Ltd. Published by Elsevier Inc. All rights reserved.
