- SPECIALIST DNA SERVICESInnovative services from Cellmark
- HIGH SENSITIVITY DNAA more sensitive form of DNA analysis
- MITOCHONDRIAL DNAUseful for bones, hair and degraded samples
- Y-STR DNA PROFILINGMale specific DNA analysis
- ANIMAL SPECIES TESTINGIdentifying species by mitochondrial sequencing
- COLD CASE REVIEW SERVICEUnlocking the secrets of unsolved crime
- SEXUAL OFFENCE INVESTIGATIONA specialist service that delivers results
A valuable forensic tool for investigating cases of rape and sexual assault
Cellmark provides an ISO17025 accredited Y-STR profiling service using the informative 23 STR marker system Powerplex® 23 (PPY23).
Y-STR profiling examines Short Tandem Repeat (STR) markers that are only present on the male Y chromosome. Although less statistically informative than standard autosomal STRs, it is a highly sensitive forensic technique and, because it specifically targets male DNA, it is particularly useful for detecting and analysing a male suspect’s DNA in a sample which contains a mixture of male and female cellular material. It is also a very useful technique for determining the number of men that have contributed to a mixed sample, as well as for linking male relatives.
An individual's Y-STR profile is inherited from father to son so that all male descendants have essentially the same Y-STR profile. It is therefore a very useful technique for relationship analysis: for linking, or excluding, male relatives. PPY23 includes two rapidly mutating Y-STR loci to assist with differentiating close male relatives.
In sexual offence investigations it is not uncommon for samples to have a mixture of male and female DNA, particularly intimate swabs taken from a female complainant. When a mixed sample contains only trace levels of male DNA and a very large amount of female cellular material, this can have the effect of masking the male DNA if analysed using autosomal STRs (despite the use of techniques to separate spermatazoa from epithelial cells). However, the sensitivity of Y-STR profiling allows the detection of even a very minor male component.
In 2014 Cellmark published a study of sexual offence cases (including allegations of digital penetration) where intimate swabs had been taken but no semen had been detected, and where there had been no indication of a male contributor in the autosomal STR results. In this study Y-STR information was obtained in over 20% of cases. This, together with other international studies, provides compelling support for the inclusion of Y-STR profiling, together with Cellmark’s specialist recovery, extraction and analysis techniques, as part of a comprehensive forensic sexual offences service.