title: STR analysis of artificially degraded DNA-results of a collaborative European exercise.
abstract: 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.
authors.affiliation: Institut für Rechtsmedizin, Universität Mainz, Mainz, Germany. pschneid@uni-mainz.de
authors.forename: Peter M
authors.initials: PM
authors.lastname: Schneider
authors.forename: Klaus
authors.initials: K
authors.lastname: Bender
authors.forename: Wolfgang R
authors.initials: WR
authors.lastname: Mayr
authors.forename: Walther
authors.initials: W
authors.lastname: Parson
authors.forename: Bernadette
authors.initials: B
authors.lastname: Hoste
authors.forename: Ronny
authors.initials: R
authors.lastname: Decorte
authors.forename: Jan
authors.initials: J
authors.lastname: Cordonnier
authors.forename: Daniel
authors.initials: D
authors.lastname: Vanek
authors.forename: Niels
authors.initials: N
authors.lastname: Morling
authors.forename: Matti
authors.initials: M
authors.lastname: Karjalainen
authors.forename: C
authors.initials: C
authors.lastname: Marie-Paule Carlotti
authors.forename: Myriam
authors.initials: M
authors.lastname: Sabatier
authors.forename: Carsten
authors.initials: C
authors.lastname: Hohoff
authors.forename: Hermann
authors.initials: H
authors.lastname: Schmitter
authors.forename: Werner
authors.initials: W
authors.lastname: Pflug
authors.forename: Rainer
authors.initials: R
authors.lastname: Wenzel
authors.forename: Dieter
authors.initials: D
authors.lastname: Patzelt
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Lessig
authors.forename: Peter
authors.initials: P
authors.lastname: Dobrowolski
authors.forename: Geraldine
authors.initials: G
authors.lastname: O'Donnell
authors.forename: Luciano
authors.initials: L
authors.lastname: Garafano
authors.forename: Marina
authors.initials: M
authors.lastname: Dobosz
authors.forename: Peter
authors.initials: P
authors.lastname: De Knijff
authors.forename: Bente
authors.initials: B
authors.lastname: Mevag
authors.forename: Ryszard
authors.initials: R
authors.lastname: Pawlowski
authors.forename: Leonor
authors.initials: L
authors.lastname: Gusmão
authors.forename: Maria
authors.initials: M
authors.lastname: Conceicao Vide
authors.forename: Antonio
authors.initials: A
authors.lastname: Alonso Alonso
authors.forename: Oscar
authors.initials: O
authors.lastname: García Fernández
authors.forename: Pilar
authors.initials: P
authors.lastname: Sanz Nicolás
authors.forename: Ann
authors.initials: A
authors.lastname: Kihlgreen
authors.forename: Walter
authors.initials: W
authors.lastname: Bär
authors.forename: Verena
authors.initials: V
authors.lastname: Meier
authors.forename: Anne
authors.initials: A
authors.lastname: Teyssier
authors.forename: Raphael
authors.initials: R
authors.lastname: Coquoz
authors.forename: Conxita
authors.initials: C
authors.lastname: Brandt
authors.forename: Ursula
authors.initials: U
authors.lastname: Germann
authors.forename: Peter
authors.initials: P
authors.lastname: Gill
authors.forename: Justine
authors.initials: J
authors.lastname: Hallett
authors.forename: Matthew
authors.initials: M
authors.lastname: Greenhalgh
mesh_terms: 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
chemical_list: D004247:DNA