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 evid entiary value in forensic casework. Chelex-extracted DNA from 115 spec imens (105 dried blood standards and 10 casework samples) was amplifie d for specific ZFX and ZFY regions of the X and Y chromosomes and subs equent restriction enzyme digestion. The polymerase chain reaction (PC R) yielded a 209 base pair (bp) product containing a polymorphic posit ion with a Y chromosome portion including an additional Hae III restri ction site while the X chromosome portion contains only one. The diges ted PCR product was separated by polyacrylamide gel electrophoresis (P AGE) and detected by silver staining. Female samples exhibit bands of 172 bp and 37 bp only while male samples (XY) exhibit 2 additional ban ds appearing as an 88/84 bp doublet. Initially the 105 known bloodstai ns were typed according to the procedure discussed here and correct ge nder determination was achieved for all samples therefore establishing the reliability of this method. The 10 casework samples yielded the e xpected results as well. This assay demonstrates potential in both pre sumptive and confirmatory capacities.