On the Forensic Use of Y-Chromosome Polymorphisms

[NathanS]

On the Forensic Use of Y-Chromosome Polymorphisms
by Peter de Knijff
Genes 2022, 13(5), 898; https://doi.org/10.3390/genes13050898

Abstract
Nowadays, the use of Y-chromosome polymorphisms forms an essential part of many forensic DNA investigations. However, this was not always the case. Only since 1992 have we seen that some forensic scientists started to have an interest in this chromosome. In this review, I will sketch a brief history focusing on the forensic use of Y-chromosome polymorphisms. Before describing the various applications of short-tandem repeats (STRs) and single nucleotide polymorphisms (SNPs) on the Y-chromosome, I will discuss a few often ignored aspects influencing proper use and interpretation of Y-chromosome information: (i) genotyping Y-SNPs and Y-STRs, (ii) Y-STR haplotypes shared identical by state (IBS) or identical by descent (IBD), and (iii) Y-haplotype database frequencies.

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Conclusions
I hope that from the above it will become clear that, in contrast to common belief, the use of Y-chromosome polymorphic markers in a forensic context is not for the faint-hearted. Nothing is as it seems, and, in contrast to an autosomal STR profile, Y-STR profiles (haplotypes) will—rare cases excepted—not be individual specific. There will always be an unknown number of males with a similar profile. As a consequence, a Y-haplotype frequency (no matter how it is estimated) has a different evidential value. Nevertheless, the use of Y-chromosome polymorphisms can be a very powerful forensic research tool, if used and interpreted with care. Especially as an exclusion tool in complex male–female crime-scene sample mixtures, it has proven to be invaluable. Furthermore, its ideal suitability as a dragnet facilitator has demonstrated its usefulness. As one of the initiators of the use of Y-chromosome STRs in forensics, I strongly support the recommendations as outlined in the various ISFG publications on this topic [63]. However, as an independent scientist, I sometimes have slightly different opinions. These, I have tried to explain above.

[Farroukh]

Собственно, криминалисты пришли к тому же, что и мы. Короткие гаплотипы (речь про Yfiler и его разновидности, 17- или 27-маркёрные гаплотипы) в ряде популяций не являются абсолютно уникальными. Что и говорить, полным совпадением с преступником по игреку вполне может быть весь его род, начиная от родного брата до десятиюродного дедушки