STR analysis of artificially degraded DNA-results of a collaborative European exercise.
Degradation of human DNA extracted from forensic stains is, in most cases, the result of a natural process due to the exposure of the stain samples to the environment. Experiences with degraded DNA from casework samples show that every sample may exhibit different properties in this respect, and that it is difficult to systematically assess the performance of routinely used typing systems for the analysis of degraded DNA samples. Using a batch of artificially degraded DNA with an average fragment size of approx. 200 bp a collaborative exercise was carried out among 38 forensic laboratories from 17 European countries. The results were assessed according to correct allele detection, peak height and balance as well as the occurrence of artefacts. A number of common problems were identified based on these results such as strong peak imbalance in heterozygous genotypes for the larger short tandem repeat (STR) fragments after increased PCR cycle numbers, artefact signals and allelic drop-out. Based on the observations, strategies are discussed to overcome these problems. The strategies include careful balancing of the amount of template DNA and the PCR cycle numbers, the reaction volume and the amount of Taq polymerase. Furthermore, a careful evaluation of the results of the fragment analysis and of automated allele calling is necessary to identify the correct alleles and avoid artefacts.
Schneider
Peter M
PM
Institut für Rechtsmedizin, Universität Mainz, Mainz, Germany. pschneid@uni-mainz.de
Bender
Klaus
K
Mayr
Wolfgang R
WR
Parson
Walther
W
Hoste
Bernadette
B
Decorte
Ronny
R
Cordonnier
Jan
J
Vanek
Daniel
D
Morling
Niels
N
Karjalainen
Matti
M
Marie-Paule Carlotti
C
C
Sabatier
Myriam
M
Hohoff
Carsten
C
Schmitter
Hermann
H
Pflug
Werner
W
Wenzel
Rainer
R
Patzelt
Dieter
D
Lessig
Rüdiger
R
Dobrowolski
Peter
P
O'Donnell
Geraldine
G
Garafano
Luciano
L
Dobosz
Marina
M
De Knijff
Peter
P
Mevag
Bente
B
Pawlowski
Ryszard
R
Gusmão
Leonor
L
Conceicao Vide
Maria
M
Alonso Alonso
Antonio
A
García Fernández
Oscar
O
Sanz Nicolás
Pilar
P
Kihlgreen
Ann
A
Bär
Walter
W
Meier
Verena
V
Teyssier
Anne
A
Coquoz
Raphael
R
Brandt
Conxita
C
Germann
Ursula
U
Gill
Peter
P
Hallett
Justine
J
Greenhalgh
Matthew
M
D000483:Alleles; D019411:Clinical Laboratory Techniques / Q000592:standards*; D003299:Cooperative Behavior; D004247:DNA / Q000032:analysis; D016172:DNA Fingerprinting / Q000592:standards*; D053938:DNA Fragmentation; D005060:Europe; D006801:Humans; D016133:Polymerase Chain Reaction / Q000379:methods* / Q000706:statistics & numerical data; D020080:Tandem Repeat Sequences
D004247:DNA