A.B. Agellon, B. Coullahan, M. Stumpf, S.D. Narveson, and M.F. Hammer
Laboratory of Molecular Systematics and Evolution, Division of Biotechnology, University of Arizona, Tucson

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It is anticipated that the development of the human Y chromosome as a forensic tool will have a dramatic impact on the analysis of samples associated with violent crimes, such as sexual assault. Cases of sexual assault currently comprise approximately 75% of forensic casework in which there is biological evidence for examination. The development of a Y chromosome-based forensic testing system, will permit a more rapid analysis of the mixed body fluid stains associated with these cases by eliminating the need for the differential extraction of male and female cells. To test the potential of the Y chromosome to differentiate individuals, we have genotyped four Y-lined short tandem repeats (STRs) in a diverse sample of 74 males, representing five major human geographic groups. A total of 23 alleles were identified at the four loci: six at DYS19, six at DYS389-I, seven at DYS390, and four at DYS391. Allelic variation at these four loci yielded a total of 64 "combination" haplotypes, with a heterozygosity of 0.995+0.000 in the world sample. Heterozygosities ranged from 0.911+0.025 in the Native American sample (n=10), to 0.982+0.004 in the Asian sample (n=26), to 0.993+0.005 in the African sample (n=18), to 1.00+0.022 and 1.00+0.010 in the Australasian (n=8) and Caucasian (n=12) samples, respectively. Three haplotypes were shared between Asians and other geographic groupings: haplotype 9 with Australasians, haplotype 13 with Caucasians, and haplotype 14 with Africans. Four haplotypes were found to be shared within major groupings. Four individuals carrying haplotype 17 were found in one Asian sub-population (Yakut) and two Africans from one sub-population (Khoisan) were found with haplotye 60. Within Native Americans, two individuals from the same tribe (Surui) had haplotype 43 and three individuals had haplotype 44. Preliminary data from additional Y-linked STRs indicate that some of these "shared" haplotypes can be further resolved into separate combination haplotypes. Therefore, we conclude that the Y chromosome is extremely variable in human populations and could be utilized as a powerful forensic tool.