Original scientific paper
Validity of Low Copy Number Typing and Applications to Forensic Science
Bruce Budowle
; Department of Forensic and Investigative Genetics, University of North Texas Health Science Center, Ft Worth, Tex, USA
Arthur J. Eisenberg
; Department of Forensic and Investigative Genetics, University of North Texas Health Science Center, Ft Worth, Tex, USA
Angela van Daal
; Faculty of Health Science & Medicine, Bond University, Gold Coast, Qld, Australia
Abstract
Low copy number (LCN) typing, particularly for current
short tandem repeat (STR) typing, refers to the analysis
of any sample that contains less than 200 pg of template
DNA. Generally, LCN typing simply can be defined as the
analysis of any DNA sample where the results are below
the stochastic threshold for reliable interpretation. There
are a number of methodologies to increase sensitivity of
detection to enable LCN typing. These approaches encompass
modifications during the polymerase chain reaction
(PCR) and/or post-PCR manipulations. Regardless
of the manipulations, when processing a small number of
starting templates during the PCR exaggerated stochastic
sampling effects will occur. The result is that several phenomena
can occur: a substantial imbalance of 2 alleles at
a given heterozygous locus, allelic dropout, or increased
stutter. With increased sensitivity of detection there is a
concomitant increased risk of contamination. Recently, a
commission reviewed LCN typing and found it to be “robust”
and “fit for purpose.” Because LCN analysis by its nature
is not reproducible, it cannot be considered as robust
as that associated with conventional DNA typing. The findings
of the commission seem inconsistent with the nature
of LCN typing. While LCN typing is appropriate for identification
of missing persons and human remains and for
developing investigative leads, caution should be taken
with its use in other endeavors until developments are
made that overcome the vagaries of LCN typing. A more
in-depth evaluation by the greater scientific community
is warranted. The issues to consider include: training and
education, evidence handling and collection procedures,
the application or purpose for which the LCN result will be
used, the reliability of current LCN methods, replicate analyses,
interpretation and uncertainty, report writing, validation
requirements, and alternate methodologies for better
performance
Keywords
Forensic Science; DNA; Low Copy Number; PCR; Stochastic Effects; Allele Drop-out; Allele Drop-in; Stutter, Validation; Robustness; Methodologies; Investigative Lead
Hrčak ID:
40669
URI
Publication date:
15.6.2009.
Visits: 5.670 *