A new federal DNA quality assurance standard will help forensic and medical laboratories ensure that DNA profiles made by the fastest and most popular profiling method are accurate.
The new DNA quality assurance standard, known as Standard Reference Material 2391–PCR-based DNA Profiling Standard, was developed by the National Institute of Standards and Technology and the National Institute of Justice. It will allow laboratories to verify the accuracy of DNA analyses using the polymerase chain reaction method of profiling.
The polymerase chain reaction, or PCR, method allows scientists to quickly copy and profile tiny amounts of DNA. Developed by Cetus Corp. in 1985, PCR is a favored way to analyze DNA because it gives results in a few hours rather than weeks as earlier DNA profiling methods require.
"PCR technology has revolutionized molecular biology. It is speeding up medical research, and with the issuance of this new profiling standard, designed specifically for forensic and paternity testing, accuracy now can be assessed in each laboratory performing analyses," says Dennis J. Reeder, leader of the DNA Technologies Group in the Biotechnology Division of NIST's Chemical Science and Technology Laboratory.
Reeder developed the PCR-based DNA profiling SRM with research biologist Margaret C. Kline and physical science technician Janette W. Redman. Jennifer C. Colbert, project manager, of the NIST Standard Reference Materials Program coordinated the preparation of SRM 2391. Funding was provided from the National Institute of Justice through the NIST Office of Law Enforcement Standards and the NIST Standard Reference Materials Program.
DNA, short for deoxyribonucleic acid, is the long spiral- shaped molecule that contains the unique set of genes which determines an individual's physical traits from hair and eye color to height and foot size. No two people, other than identical twins, have the same genetic sequence encoded in their DNA.
In addition to its speed, another advantage of the PCR technique is that it gives accurate results with tiny amounts of DNA, such as a suspect might leave in saliva on a cigarette butt or postage stamp. PCR is analogous to a molecular copying machine. It allows laboratories to accurately reproduce DNA from a single cell thousands of times. Older methods of DNA profiling can not reproduce DNA strands and require larger numbers of cells. PCR also offers enhanced sensitivity, reduced cost and makes it possible to profile DNA from degraded forensic samples.
The PCR method of DNA profiling allows biomedical researchers to speed up dramatically studies on genetics and disease. The technology also is used for identification in both paternity and criminal cases, such as rape or murder. PCR-based DNA profiles are gaining acceptance in courtrooms around the country, but standards are needed for universal acceptance.
NIST issued the first DNA Profiling Standard, SRM 2390, in 1992. This standard was designed for the restriction fragment length polymorphism, or RFLP, method of DNA profiling, which is currently the most widely used method of profiling DNA for criminal or civil cases. PCR-based DNA profiling is as accurate and precise as the RFLP method and has been used successfully in several criminal trials. The availability of the new profiling standard should help PCR methods continue to gain wide acceptance in the legal community.
The PCR profiling standard comes with 20 components, including eight vials of well-characterized human DNA, four vials of PCR-amplified DNA and two genetic ladders for measuring DNA fragments from 100 to 1,500 base pairs in length. The standard also includes two human cell lines to provide cells from which DNA can be extracted. Also included are sets of extracted DNA from the same cell lines, as well as PCR-amplified DNA from the same cell lines and other samples. Two companies, Roche Molecular Systems, Alameda, Calif., and Life Technologies Inc., Gaithersburg, Md., provided the source components.
Laboratories can perform their own DNA profiles on the components in the NIST profiling standard. Results agreeing with the certified values from NIST indicate that a laboratory is performing the analysis accurately. If the laboratory's results differ, the NIST profiling standard can help identify where problems are occurring.
The DNA in SRM 2391 was analyzed at NIST and by 20 federal, state and commercial laboratories in the United States as well as three foreign laboratories. Three rounds of interlaboratory testing verified the profiles of the DNA in the NIST SRM.
NIST's PCR-based DNA Profiling Standard, SRM 2391, is available for $409 plus shipping from the NIST Standard Reference Materials Program, 204 Engineering Mechanics Building, Gaithersburg, Md. 20899-0001, (301) 975-6776, fax: (301) 948- 3730.
As a non-regulatory agency of the Commerce Department's Technology Administration, NIST promotes U.S. economic growth by working with industry to develop and apply technology, measurements and standards.