Restriction Fragment Length Polymorphism (RFLP) Analysis on DNA from Human Compact Bone

Abstract

DNA typing techniques primarily identify specific genetic markers that are highly polymorphic within a population and have found great utility in forensic science. The established DNA identification protocol, termed restriction fragment length polymorphism (RFLP), has been admitted as physical evidence in the investigation of crimes such as assault, sexual assault, and homicide. The limitation associated with this procedure concerns the integrity of the genetic material. This study sought to evaluate human bone as a source material for DNA identification following exposure to common forensic field conditions. Often, with the onset of decomposition and eventual disarticulation of a body, soft tissues, hair and teeth may not be recovered. The significance of this study lies in the fact that, within forensic anthropology, human bone represents the most biologically stable evidence and is sometimes all that remains after periods of exposure. Genomic DNA was extracted from human bone following exposure to surface deposit, shallow burial, and fresh water immersion. Samples were collected over a three month time course and analyzed by spectrophotometry and agarose gel electrophoresis as well as RFLP analysis. The data suggest that high molecular weight DNA may indeed be extracted from human bone and typed by RFLP analysis for use in forensic identification. Under simulated forensic field conditions, the severity of DNA degradation was in the order of fresh water immersion > shallow burial > surface deposit. Genomic DNA from bone deposited on the desert surface for up to 4 weeks was detected by RFLP analysis. No spurious bands were detected in any specimens, and to the extent that bands were still present, the RFLP patterns matched. These findings demonstrate that human bone can be a reliable source of genomic DNA, and that bone recovered from surface deposit is the most desirable for use in forensic identification.