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1. Introduction
DNA can be successfully extracted from many biological
sources such as blood, semen, saliva and skin cells. This DNA
can then be amplified using PCR to create DNA profiles which could
be used to Giúp convict or exonerate a suspect in a criminal case,
therefore DNA is vital in forensic science. Extraction methods not
only have to ensure that DNA is efficiently extracted from each
sample, they also have to remove inhibitors which may interfere
with subsequent downstream processes. For example, blood
contains haem which is a PCR inhibitor and therefore this must
be sufficiently removed during the extraction process to allow the
DNA to be amplified [1]. Both organic and inorganic methods of
DNA extraction are available, each giving variable results
depending on the sample type.
Chelex1-100 (Bio-Rad Laboratories, CA, USA) is a chelating
resin which uses ion exchange to bind transition metal ions. The
resin is composed of styrene divinylbenzene copolymers contain
ing paired iminodiacetate ions, which act as chelators for
polyvalent metal ions [2]. During the extraction process, the
alkalinity of the solution and the act of boiling the solution breaks
down the cells and allows the chelating groups to bind to the
cellular components, protecting the DNA from degradation. The
Chelex method is a favoured extraction method as it is quick, it
does not require multiple tube transfers and it does not use toxic
organic solvents such as phenol–chloroform [1], however it is
unable to remove inhibitors (such as haem) which can be
detrimental to downstream processes.
The QIAamp DNA Investigator Kit protocol follows four main
steps: disruption of cellular membranes using a combination of
enzymatic activity and mechanical lysis (heating and shaking);
binding of DNA to the silica-based membrane of the QIAamp spin
column; washing of contaminants through the membrane using
buffers; and DNA elution. The QIAamp spin columns in this kit can
be used manually by an operator or the protocol can be automated
using the QIAcube robot [3]. The silica-based method is a robust
way of DNA extraction, removing inhibitors from the sample
whilst maintaining a high yield of good quality DNA.
DNA quantification was carried out using a real time PCR
system that allows simultaneous quantification of total autosomal
and male DNA by amplification of a 99 bp target on chromosome
17 and a 133 bp target on the Y-chromosome [4]. The kit also
includes an internal PCR control (IPC) which allows PCR inhibition
to be identified within a sample. STR profiling was carried out
using the AmpFlSTR SGM PlusTM amplification kit, which amplifies
ten STR loci and the amelogenin locus for sex determination [5].
This report will investigate the amount, and quality of, DNA
extracted from blood stains and buccal cell suspensions using the
Chelex method [2], the QIAamp DNA Investigator Kit (QIAGEN,
Crawley, UK) [3] and the QIAcube instrument (QIAGEN, Crawley,
UK) [3].
y
Received 22 September 2010
Received in revised form 19 April 2011
Accepted 27 April 2011
Keywords:
DNA extraction
Real-time PCR
Chelex
Qiagen
STR profiling
ple is the basis for successful forensic DNA profiling. There are many
DNA extraction methods available and they vary in their ability to efficiently extract the DNA; as well as
in processing time, operator intervention, contamination risk and ease of use. In recent years, automated
robots have been made available which speed up processing time and decrease the amount of operator
input. This project was set up to investigate the efficiency of three DNA extraction methods, two manual
(Chelex1-100 and the QIAGEN DNA Investigator Kit) and one automated (QIAcube), using both buccal
cells and blood stains as the DNA source. Extracted DNA was quantified using real-time PCR in order to
assess the amount of DNA present in each sample. Selected samples were then amplified using AmpFlSTR
SGM Plus amplification kit. The results suggested that there was no statistical difference between results
gained for the different methods investigated, but the automated QIAcube robot made sample
processing much simpler and quicker without introducing DNA contamination.
 2011 Published by Elsevier Ireland Ltd.
* Corresponding author. Tel.: +44 141 548 2500; fax: +44 141 548 2532.
E-mail addresses: [email protected], [email protected]
(L. Welch).
1872-4973/$ – see front matter  2011 Published by Elsevier Ireland Ltd.
doi:10.1016/j.fsigen.2011.04.018

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