Implementation of Y-STR Analysis by Biology Services

On 2018-07-19, the National Forensic Laboratory Services (NFLS) is implementing Y Chromosome Short Tandem Repeat (Y-STR) analysis using the Yfiler™ Plus PCR Amplification Kit.

Y-STR analysis focuses on STRs found on the Y chromosome, only carried by male individuals. Y-STR analysis could be useful in cases where samples contain a mixture of male and female DNA and there is an overabundance of female DNA (e.g., sexual assault). Since female individuals do not possess a Y chromosome, this difference allows for the male DNA to be targeted in such mixtures. In specific instances, the use of Y-STR analysis may increase the chance of detecting trace male contributions, generating results not possible using conventional autosomal STR analysis.

Considerations and limitations for Y-STR Analysis:

• Autosomal STR analysis has greater power of discrimination than Y-STR analysis.

• Males from the same paternal lineage share the same Y chromosome; the Yfiler™ Plus PCR Amplification Kit targets some Y-STRs with an increased mutation rate that could help differentiate related males in some cases.

• Y-STR profiles cannot be searched against the National DNA Data Bank of Canada.

For the above reasons, requests for Y-STR analysis will be assessed on a case-by-case basis. Only cases meeting the following criteria will be considered for Y-STR analysis:

• Male persons of interest have been identified; known reference samples will be required for comparison purposes.

• Autosomal STR analysis could not generate a male profile suitable for comparison

• Male DNA must be in sufficient quantity for Y-STR analysis (as determined by the laboratory); the minimum amount of male DNA required for Y-STR analysis is 150 picograms.

In order to monitor the anticipated volume of submissions, NFLS Biology Services will initially only accept cases that were processed by the laboratory after August 2014, coinciding with the introduction of a new quantification system allowing reliable male DNA quantification.