Sex Determination of Dried Blood Stains Using the Polymerase Chain Reaction (PCR) with Homologous X-Y Primers of the Zinc Finger Protein Gene

The ability to “sex” unknown dried bloodstains is frequently of evidentiary value in forensic casework. Chelex-extracted DNA from 115 specimens (105 dried blood standards and 10 casework samples) was amplified for specific ZFX and ZFY regions of the X and Y chromosomes and subsequent restriction enzyme digestion. The polymerase chain reaction (PCR) yielded a 209 base pair (bp) product containing a polymorphic position with a Y chromosome portion including an additional Hae III restriction site while the X chromosome portion contains only one. The digested PCR product was separated by polyacrylamide gel electrophoresis (PAGE) and detected by silver staining. Female samples exhibit bands of 172 bp and 37 bp only while male samples (XY) exhibit 2 additional bands appearing as an 88/84 bp doublet. Initially the 105 known bloodstains were typed according to the procedure discussed here and correct gender determination was achieved for all samples therefore establishing the reliability of this method. The 10 casework samples yielded the expected results as well. This assay demonstrates potential in both presumptive and confirmatory capacities.