Sex determination of forensic samples: co-amplification and simultaneous detection of a Y-specific and an X-specific DNA sequence

The detection of restriction fragment length polymorphisms (RFLP) (1) in DNA extracted from forensic samples remains impossible in a significant number of cases due to deterioration and contamination of the biological material and the extremely low quantities of DNA isolated. The polymerase chain reaction (PCR) is a recent and particularly convenient method for analysing and typing very small amounts (10-20 ng) of degraded human DNA. DNA analysis at the level of a few cells present in forensic samples such as bloodstains, semen stains, vaginal swabs and head hair bulbs now appears possible using DNA amplification. A PCR protocol was adapted to simultaneously amplify a Y-specific DNA repeat sequence from the DYZ1 locus and an X-specific DNA repeat sequence from the DXS424 locus. The co-amplified Y-specific DNA fragment (102 bp) and X-specific DNA fragments (181-199 bp) were visualized on an ethidium bromide-stained 4% agarose gel. The male or female type of the amplified DNA extracted from blood samples, bloodstains, semen stains, vaginal swabs, brain tissue and 1, 2, 5, or 10 head hair bulbs was determined.