DNA Profiling Standard Reference Materials

Summary

NIST has produced several PCR-based DNA Profiling Standard Reference Materials (SRMs) for the forensic community. The primary uses of these materials are validation and calibration of currently used methods for quality assurance purposes. As advances in methodologies occur and new loci become accepted for use in the human identity testing community, there becomes a need to update the certified values for current SRM materials to keep pace. To that end we have updated the Certificates of Analysis for the SRM 2391b PCR-based DNA Profiling Standard and the SRM 2395 Human Y-Chromosome DNA Profiling Standard.

Description

Intended impact
This work was designed to provide materials that forensic laboratories being assessed under the FBI DNA Quality Assurance Standard can comply with as stated, "The laboratory shall check its DNA procedures annually or whenever substantial changes are made to the protocol(s) against an appropriate and available NIST standard reference material or standard traceable to a NIST standard."

Objective(s)
Provide the human identity testing community up-to-date reference materials that can be used to ensure that each laboratory is operating under calibrated conditions, enabling compatible and reliable results among laboratories. Assure the reference materials are adequate as advances in methodologies occur and new loci become accepted for use in the human identity testing community.

Goals 

• Certify SRM 2391b for 26 new STR loci and SRM 2395 for 20 new Y-STR loci.

Technical approach 
The certificate updates involved typing the SRM components with the additional loci and confirming the certified repeat numbers through extensive DNA sequencing. In many cases this work involved confirming and or defining STR repeat nomenclature for some of the new loci in both SRM 2391b and SRM2395. STR alleles were sequenced where no commercial kit was available with previously calibrated allelic ladders. SRM 2391b certificate updates included genetic typing with STR loci that can be used as mini-short tandem repeat (miniSTR) loci, which produce smaller sized polymerase chain reaction (PCR) products used for analyzing degraded DNA. Twenty-six STR loci were selected for inclusion on the updated certificate: D1GATA113E02, D1S1627, D1S1677, D2S441, D2S1776, D3S3053, D3S4529, D4S2364, D4S2408, D5S2500, D6S474, D6S1017, D8S1115, D9S1122, D9S2157, D10S1248, D10S1435, D11S4463, D12ATA63A05, D14S1434, D17S974, D17S1301, D18S853, D20S482, D20S1082, D22S1045

The SRM 2395 update includes certified or reference values for 20 new Y-STR loci chosen from a screen of more than 60 additional markers based on their informational value and availability from genetic genealogy companies. The loci include DYS449, DYS481, DYS505, DYS522, DYS532, DYS534, DYS635, DYS570, DYS576, DYS607, DYS715, and DYS717.

Major Accomplishments

• Increased the number of certified and reference value loci from 22 STR loci to 49 STR loci on SRM 2391b.
• Increased the number of certified and reference value loci from 22 STR loci to 42 STR loci on SRM 2395.
• Evaluated the stability of both SRM 2391b and SRM 2395.