Molecular Diagnostic Applications in Forensic Science

This chapter describes the general characteristics of short tandem repeats on Y chromosomes (Y-STRs) in forensic analyses, analytic procedures for typing Y-STR loci, and general interpretation issues. Y-chromosome DNA resides in the nucleus, but its markers differ in some respects from the autosomal loci. Most of the DNA in the Y-chromosome is non-recombinant, with only the most distal portions of the chromosome able to recombine with the X-chromosome. Barring mutation, the Y-linked DNA types are identical for all paternal relatives, including male siblings. This characteristic is helpful in human identity cases, such as those involving the analysis of the remains of a missing person. In such cases, known paternal relatives can provide reference samples for direct comparison to the unknown Y-linked DNA types. A set of markers residing on the Y-chromosome enable the analysis of samples, such as mixtures composed of minute amounts of male DNA amid a large background of female DNA. Issues to be considered when implementing DNA typing methods for Y-STRs are exemplified and core sets of Y-STR loci are defined. Molecular diagnostic applications in forensic science require the methods to be validated and developed for placing statistical weight on an evidence profile that matches a reference sample profile, quality assurance measures to be implemented, and interpretation guidelines instituted.