Abstract:
Touch DNA, also known as Trace DNA, is an important aspect of
criminal investigations, as the perpetrator is unaware of the DNA they have
left behind. While there are multiple ways to extract touch DNA, it has been
established that direct amplification provides exemplary results. Direct
Amplification is the process of analyzing the samples by amplifying them
without extraction or quantitation. However, there is no measure on how much
information direct amplification provides as opposed to other widely used
methods including standard extraction procedures. This study aimed to look at
the differences in information obtained when processing a touch DNA sample
using standard extraction procedures versus a direct amplification approach.
Understanding the scope of information collected by direct amplification
versus standard extraction procedures can be used to facilitate new protocols
for processing touch DNA. This study focused on collecting touch DNA samples
from 20 volunteers and processing the DNA using two methods. In the first
half of the study, half of the samples were extracted, quantified, and
amplified using the InnoXtractTM, InnoQuantTM and InnoTyperTM kits,
respectively, from InnoGenomics, LLC. The next part of the study included
adding swabs to be directly amplified using the InnoTyperTM 21 kit. Rather
than the standard extraction protocol, this method included placing the swab
heads directly into the PCR tubes for amplification. Samples undergoing
direct amplification are expected to show more information due to the fact
that standard extraction protocols often result in loss of DNA. Data
generated from capillary electrophoresis was compared by reviewing the allele
peak heights. Samples exhibiting “real” and representative peaks were
further reviewed to determine if the peaks were real or due to artifacts such
as noise. The research findings may lead to revised protocols that can be
applied to difficult sample types, such as touch DNA, which often result in
partial DNA profiles that often contain very little information.