16 Y-Specific STR Analysis in Human  Remains Identification

Vieira-Silva, Cláudia; Cruz, C.; Ribeiro, Teresa; Lucas, Isabel; Geada, H.; Espinheira, R.

http://hdl.handle.net/10400.26/44052

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Authors

Vieira-Silva, Cláudia

Abstract(s)

Forensic investigation often requires the use of degraded biological material, especially for determining the identity of human remains. Y-STRs, offer new perspectives for identification and kinship analysis especially on forensic deficiency cases 1 in complement of autosomal STRs. The non-recombining portion of the Y-chromosome is of value providing additional data in paternal lineage identification. The aim was the study of 16 Y-STR loci to perform human remains identification - the minimal Y-STR haplotype - DYS19, DYS390, DYS391, DYS392, DYS393, DYS19, DYS389I/II, DYS385 – and – GATA A .1(DYS460), GATA A 7.2 (DYS461), GATA C4, GATA H4, DYS437, DYS438, DYS439 loci, that are part of the Y-chromosome quality control Group of the Spanish and Portuguese Group (GEPY) of the ISFG. Y-STR typing in degraded biological material has major technical challenges since each sample has unique characteristics. The best results were obtained in autopsy bloodstains may be due to the fact that the autolysis mechanisms are still incipient. Otherwise blood kept at 4º C for more than a year didn’t provide the same good results. Liquid blood samples from deceased individuals may contain porfirinic compounds from hemoglobin, powerful PCR inhibitors difficult to eliminate9. In bone and teeth samples the source of inhibitors may be a high amount of DNA from other micro-organisms such as bacteria and fungi which invade bone9 and probably this kind of contaminants can explain some of the results obtained in bones and teeth samples submitted to prolonged humidity, temperature environmental conditions and also adverse soil characteristics. The problem with the studied samples seems not to be DNA quantity but the out-of-control presence of inhibitors that interfere not only with the extraction but also with the amplification process because most of the results were obtained with a dilution of DNA extraction and adding more Taq, sometimes 2 or 3 fold. With these samples, it seems that the success or failure depends on each sample itself and it should be treated individually. The number of distinct factors connected to each sample is difficult to calculate, so it is necessary to make a few attempts in order to have as many results as possible.