title: Assessing PreCR™ repair enzymes for restoration of STR profiles from artificially degraded DNA for human identification.
abstract: Forensic scientists have used several approaches to obtain short tandem repeat (STR) profiles from compromised DNA samples, including supplementing the polymerase chain reaction (PCR) with enhancers and using procedures yielding reduced-length amplicons. For degraded DNA, the peak intensities of the alleles separated by electrophoresis generally decrease as the length of the allele increases. When the intensities of the alleles decrease below an established threshold, they are described as drop-outs, thus contributing to a partial STR profile. This work assesses the use of repair enzymes to improve the STR profiles from artificially degraded DNA. The commercial PreCR™ repair kit of DNA repair enzymes was tested on both purified DNA and native DNA in body fluids exposed to oxidizing agents, hydrolytic conditions, ultraviolet (UV) and ionizing radiation, and desiccation. The strategy was to restrict the level of DNA damage to that which yields partial STR profiles in order to test for allele restoration as opposed to simple allele enhancement. Two protocols were investigated for allele restoration: a sequential protocol using the manufacturer's repair procedure and a modified protocol reportedly designed for optimal STR analysis of forensic samples. Allele restoration was obtained with both protocols, but the peak height appeared to be higher for the modified protocol (determined by Mann-Kendall Trend Test). The success of the approach using the PreCR™ repair enzymes was sporadic; it led to allele restoration as well as allele drop-out. Additionally, allele restoration with the PreCR™ enzymes was compared with restoration by alternative, but commonly implemented approaches using Restorase™, PCRBoost™, bovine serum albumin (BSA) and the Minifiler™ STR system. The alternative methods were also successful in improving the STR profile, but their success also depended on the quality of the template encountered. Our results indicate the PreCR™ repair kit may be useful for restoring STR profiles from damaged DNA, but further work is required to develop a generalized approach.
authors.affiliation: Counterterrorism and Forensic Science Research Unit, Federal Bureau of Investigation Laboratory Division, 2501 Investigation Parkway, Quantico, VA 22135, United States. Electronic address: james.m.robertson@ic.fbi.gov.
authors.forename: James M
authors.initials: JM
authors.lastname: Robertson
authors.affiliation: Counterterrorism and Forensic Science Research Unit, Visiting Scientist Program, Federal Bureau of Investigation Laboratory Division, 2501 Investigation Parkway, Quantico, VA 22135, United States.
authors.forename: Shauna M
authors.initials: SM
authors.lastname: Dineen
authors.affiliation: Counterterrorism and Forensic Science Research Unit, Visiting Scientist Program, Federal Bureau of Investigation Laboratory Division, 2501 Investigation Parkway, Quantico, VA 22135, United States.
authors.forename: Kristina A
authors.initials: KA
authors.lastname: Scott
authors.affiliation: Counterterrorism and Forensic Science Research Unit, Visiting Scientist Program, Federal Bureau of Investigation Laboratory Division, 2501 Investigation Parkway, Quantico, VA 22135, United States; Armed Forces DNA Identification Laboratory, Armed Forces Medical Examiner System, 115 Purple Heart Ave., Dover Air Force Base, Dover, DE 19902, United States; American Registry of Pathology, P.O. Box 495, Dover, DE 19903, United States.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Lucyshyn
authors.affiliation: Counterterrorism and Forensic Science Research Unit, Visiting Scientist Program, Federal Bureau of Investigation Laboratory Division, 2501 Investigation Parkway, Quantico, VA 22135, United States.
authors.forename: Maria
authors.initials: M
authors.lastname: Saeed
authors.affiliation: Counterterrorism and Forensic Science Research Unit, Visiting Scientist Program, Federal Bureau of Investigation Laboratory Division, 2501 Investigation Parkway, Quantico, VA 22135, United States.
authors.forename: Devonie L
authors.initials: DL
authors.lastname: Murphy
authors.affiliation: Counterterrorism and Forensic Science Research Unit, Visiting Scientist Program, Federal Bureau of Investigation Laboratory Division, 2501 Investigation Parkway, Quantico, VA 22135, United States.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Schweighardt
authors.affiliation: Counterterrorism and Forensic Science Research Unit, Visiting Scientist Program, Federal Bureau of Investigation Laboratory Division, 2501 Investigation Parkway, Quantico, VA 22135, United States.
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Meiklejohn
mesh_terms: D004260:DNA Repair; D018732:Forensic Anthropology; D006801:Humans; D018895:Microsatellite Repeats
keywords: DNA repair; Degraded DNA; Degraded DNA reference sample; Forensic biology; PreCR™ Repair Mix; Short tandem repeat (STR) analysis