Repair of Damaged DNA for Forensic Analysis

• NCJ Number: 227498
• Author(s): John Nelson Ph.D.
• Date Published: October 2008
• Length: 95 pages
• Grant Number(s): 2006-DN-BX-K018
• Agencies: NIJ-Sponsored
• Publication Type: Report (Study/Research)

Annotation

This report describes the development of a DNA repair method that can be used on damaged DNA samples, so as to allow forensic investigators to examine evidence samples to their fullest potential, leading to more samples yielding accurate, usable results.

Abstract

The repair method uses a mixture of DNA repair enzymes to repair or replace damaged strand segments in damaged DNA. The researchers developed an optimized mix of the enzymes - DNA ligase, various glycosylases and AP endonucleases, and DNA polymerase - that can be added to DNA that contains any of a variety of damaged bases. After a simple incubation - during which the damage to the DNA is identified, removed, and sealed - the resulting sample is moved to a variety of DNA analysis procedures, including PCR analysis of STR loci. As a highly complex molecule, DNA can be damaged in a number of ways, resulting in breaks in the strands, removal, or chemical alteration of the nucleotide bases. The severity of damage to DNA can vary, but once there are one or more lesions in the DNA strands within the segment to be amplified by PCR, the amplification and analysis will fail; however, DNA is double-stranded and thus redundantly structured; nature has devised a collection of mechanisms for repairing many kinds of damage, often using the information in one DNA strand to reconstruct the other. In facilitating such repair, the proposed method of repair is designed to function after DNA isolation and quantification, but prior to DNA amplification and STR analysis. 37 figures, 9 tables, and a listing of 4 forums/media in which research results have been disseminated