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Advances
in DNA Analyses
Scientists are slowly identifying the remains of additional victims of the Sept. 11, 2001 terrorist attacks on the World Trade Center (WTC) in New York, thanks in part to a new tool for genetic analysis developed with assistance from the National Institute of Standards and Technology (NIST) and funding from the National Institute of Justice (NIJ). Sixteen additional victims have been identified so far this year in a painstaking process using new methods for analyzing unusually small segments of DNA. Remains from about half of the approximately 2,800 victims of the September 2001 attack were identified previously, many through standard analyses of DNA in tissue samples recovered from the site. Identification of many of the remaining samples continues but is difficult because of the damaged and degraded condition of the samples. One of the new techniques being used is based on a NIST-developed concept that reduces the size of DNA fragments needed for a definitive analysis. Conventional forensic methods using short tandem repeats (STRs) analyze DNA fragments from 13 specific locations within the human genome. Each fragment contains approximately 200 to 400 pairs of the nitrogen-containing compounds or "base pairs" that comprise the genetic code of an individual. The NIST approach uses "mini-STR assays" with fragments that come from the same 13 locations but are substantially smaller, with roughly 25 to 190 fewer base pairs depending on the location. The smaller size means that damaged or degraded DNA samples are more likely to have intact sections at each of the 13 specific locations. Developed by NIST chemist John Butler, the NIST approach uses new primers -- small fragments of DNA that selectively attach to specific base pair sequences. Primers allow scientists to selectively remove specific DNA fragments and then to make many copies of those fragments to create a sample large enough for reliable analysis. Butler serves with a group of internationally renowned scientists empanelled by NIJ to evaluate new technologies for use in identifying 9/11 WTC victims, the largest human identification case ever. “The miniplex concept pioneered by Dr. John Butler is responsible for the majority of the latest” identifications, said Dr. Robert Shaler, head of forensic biology for the Office of the Chief Medical Examiner in New York City. Shaler is in charge of the WTC identification effort, which is being carried out by a group of government agencies and industry contractors. For further information see this interview with John Butler. created on 5/27/03 |
