Pub. date: 2004 | Online Pub. Date: September 15, 2007 | DOI: 10.4135/9781412952415 | Print ISBN: 9780761926498 | Online ISBN: 9781412952415| Publisher:SAGE Publications, Inc.About this encyclopedia
Analysis of physical evidence left at the scene of a crime often plays a critical role in identifying the individuals who were involved in the crime. In many sexual assaults, this evidence is semen left by the perpetrator; in violent crimes it might be blood or bits of tissue from the victim or the assailant. Since 1985, an extensive effort has been made to develop laboratory procedures for DNA typing as a tool for linking such evidence to known individuals. DNA, the genetic material of humans and all other cellular organisms, consists of four small molecules, the nucleotide bases adenosine, guanosine, cytidine, and thymidine, assembled into a linear polymer. The human genome contains approximately two billion bases of DNA divided into 23 segments, called chromosomes. The order of the bases in a complete human genome has recently been determined. A person has two copies of this genome, one inherited from ...