Evaluating the informative power of Y-STRs: a comparative study using European and new African haplotype data

Abstract

Male individuals from Maputo (Mozambique) were sampled and 18 Y-STRs were typed: the nine currently used to define the “minimal haplotype” employed in the European, American and Asian “Y-STR Haplotype Reference Databases”, as well as the recently described DYS434, DYS437, DYS438, DYS439, DYS460, DYS461, GATA A10, GATA C4 and GATA H4. Allele and haplotype frequencies were estimated in a sample of 112 individuals, where it was possible to define 101 haplotypes, with an observed haplotype diversity (HD) of 0.9973. Allele diversity varied between 0.0179 and 0.9220, DYS385 showing the highest level of polymorphism and DYS392 the lowest. When considering only the most recent Y-STRs, the degree of diversity varied between 0.4011 (DYS438) and 0.6910 (GATA C4), except for DYS434 and DYS437 where a very low diversity was observed (0.0700 and 0.0526, respectively). When analysing the same 112 individuals for the nine Y-STRs included in the minimal haplotype, 78 haplotypes were distinguished with a corresponding observed diversity of 0.9884, a considerably lower value than those for Northern Portugal ( n=208; HD: 0.9925) and Macao ( n=63; HD: 0.9990). Concerning all 18 Y-STRs studied in this population, the observed diversity demonstrates their usefulness in forensic applications, with the exception of DYS434, DYS437 and DYS392. However, since the informative power of a marker has to be judged in haplotype context, a simple software, allowing the evaluation of the increase of HD through the addition of any combination of new markers to the minimum haplotype was designed. The statistical approach devised, demonstrates that an increment on HD is more rapidly obtained for the Mozambican database when adding GATA A10 or DYS439, DYS460, GATA C4, DYS461 or GATA H4, in this order, to the minimal haplotype. DYS434, DYS437 and DYS438, in conjunction with all the other 15 Y-STRs, do not contribute to an increment on HD. When applying the same approach to an European sample (Northern Portugal), the first three Y-STR choices coincide, but the next order of markers are GATA H4, then DYS437 and finally DYS461. In this sample, DYS434, DYS438 and GATA C4 do not increment HD any further.