Fourth Annual DNA Grantees' Workshop
Monday, June 23, 2003
AFTERNOON SESSION
NYC Office of the Chief Medical Examiner Experience with NIST Y-Chromosome Standard Reference Material 2395
Mechthild Prinz
Biography
MS. TOMSEY: Our next speaker is Dr. Mickey Prinz, who's the assistant director of the Department of Biology from the Office of Chief Medical Examiner, New York City. Mickey came to New York City back in 1994 as a postdoctorate fellow and decided to stay and work for the Department of Forensic Biology and the Chief Medical Examiner's Office. She cites on her bio that she appreciates working in that active environment and with the agency's amazing people.
What she doesn't say is that Mickey is one of the more amazing people at the New York City Office of Chief Medical Examiner. Through her dedication and research, she has contributed greatly to the field of forensic science.
Dr. Prinz received her master's in biology from Albertus Magnus University in Cologne, Germany, and her Ph.D. in human biology from Ulm University in Ulm, Germany.
She will be speaking to us today on her experience with the NIST (National Institute of Science and Technology) Y-chromosome SRM 2395 kit. I'd like to welcome Dr. Mickey Prinz.
DR. PRINZ: Thank you, Chris [Tomsey]. Prinz: Slide 1
What the audience doesn't know is that the speakers were asked to write their bios themselves, and since I only had 5 minutes, I kept it really short. Thanks, Chris.
We were given an advanced version of the Y–STR (Y short tandem repeat) SRM (standard reference material) to try out in our laboratory, and Tanis Garnall, the other name on my title slide, did the testing.
NIST does an amazing amount of work, as you already heard from Barbara Levin and John Butler. They have a bunch of products nobody knows about. The New York Times was writing about the NIST peanut butter standard.
NIST basically succeeded in justifying its existence by making the DNA NIST standard an undeletable item in the forensic science lab. It's written in the accreditation requirements that your DNA tests are supposed to be checked annually against an appropriate and available NIST standard. Prinz: Slide 2
It can be replaced, I guess, by NIST-traceable and we'll hear about that later. But the key word for me was the word "available," because in 1998, we went online with a Y–STR multiplex for DNA testing, and there was no NIST standard available. So I'm very happy to have SRM 2395 now. Prinz: Slide 3
To fulfil the audit requirement, we obtained sequenced reference samples from other laboratories—two laboratories in Germany and allelic ladders from Peter de Knijff, who also helped John Butler with the SRM—and we also tested the old SRM just to show good faith, which was a little bit tricky because it's mostly female.
From the SRM 2391, a PCR (polymerase chain reaction) standard, there are only four male samples. We tested them, even though the allele calls were not part of the reference material. Prinz: Slide 4
The new standard will be really helpful, I agree with John, for all labs that are starting up to fulfil the audit requirement and to calibrate their own testing. As with any of the SRM kits that we get, we requantitate them.
We requantitated them with Quantiguard. We sacrificed two microliters, and you can see the readings are in the error range that you would expect from Quantiguard. So we ignored our results, we kind of said it's close enough, and we used the NIST recommendation, the NIST quantitation value for the amplifications. Prinz: Slide 5
The allele calls, as expected, were all the way they were supposed to be. We tested three kits, Y–plex 5, Y–plex 6, and Power Y, and since these kits have allelic ladders, it's not very difficult to get the right calls. We did see the off-ladder allele for Y–plex 6. So the allele distribution is really, really nice for DYS390: five samples, five different alleles. Prinz: Slide 6
Of course, it's not as good for the other loci. The worst is 439 where you have only two alleles between the five samples. But it works very well.
I listed the peak heights I got with the different kits. I thought the audience was interested in that. With our homemade mix, we used 2 nanograms. It was really, really high. It would have worked well with 1 nanogram. The Y–plex 5 actually gave me a partial for 1 nanogram and Y–plex 6. The Power Y with 1 nanogram gave usable results on the first run. Prinz: Slide 7
So, in summary: It was 30 cycles for all of the systems, except Y–plex 5 is 32 cycles. So we feel the new SRM will be really helpful because I know a lot of laboratories will want to start Y–STR typing on sexual assault cases, and the kits are available now.
I would like to thank NIJ for the opportunity to talk here and NIST for the SRM. Thank you.
MS. TOMSEY: Thank you, Mickey.