Christian Gehrig, Manfred Hochmeister, A. Sajantila,* Urs V. Borer and Richard
Dirnhofer
Institute of Legale Medicine, University of Bern, Switzerland
*Dept. of Zoology, University of Munich, Germany
Several methods for sex determination with PCR have been described. We currently use the amelogenin gene (Mannucci et al. 1994) for sex determination of forensic samples. The advantage of this method lies in its sensitivity and its ability to determine the sex of single donor samples or a male component in mixed samples. Simultaneously it provides an internal control. However, since the amelogenin gene shows no polymorphism, this sex determination is not of much help in the DNA-profiling of mixed samples.
In the present work, we show the allele frequency distribution of 3 STR loci located on the Y chromosome, which might be useful in forensic casework. The polymorphisms of the three loci have been analyzed in a Swiss population sample of 100 unrelated males.
DYS191: a simple, well characterized system with 5 known alleles (186-202 bp; 4 bp intervals).
DYS3892: the amplification of the STR DYS389 shows two polymorphic regions (4 alleles at 250 bp and 7 alleles at 400 bp, which seem to be linked) which provides quite a high power of discrimination.
DXYS1563: the amplification of the DXYS156 showed 7 alleles (125-170 bp; 5 bp intervals). The 2 largest alleles (165 bp, 170 bp) were observed only in males, which suggest that they were amplified from the Y chromosome. The other 5 alleles were present in two copies in females and in a single copy in males, which suggest that they were amplified from the X chromosome.
It may be important to determine if a mixed sample comes from persons of opposite sex. The analysis of the 3 following Y-STR loci : DYS191, DYS389 and DXYS156 can answer this important question and provide additionally polymorphism information.
Using these Y specific STR loci we were able to exclude a suspect in a twenty year old sex-related murder case by typing male cells in a mixed sample.
REFERENCES
Roewer L., Arnemann J., Spurr N.K., Grzeschik K.H. and Epplen J.T. (1992) Simple repeat sequences on the human Y chromosome and equally polymorphic as their autosomal counterparts. Hum. Genet. 89:389-394.
Murray , JC. Probe Detail (DYS389), pers. comm.
Chen H., Lowthar W., Avramopoulos D. and Antonarakis E. (1994) Homologous Loci DXYS156X and DXYS156Y contain a polymorphic pentanucleotide repeat (TAAAA)n and map to human Y and Y chromosomes. Human Mutation 4:208-211.
Grimberg J., Nawoschik S., Belluscio L., McKee R., Turck A. and Eisenberg A. (1989) A simple and efficient nonorganic procedure for the isolation of genomic DNA from blood. Nucl. Acids Res. 17: 8390.
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