Page 47 - Academic Press Encyclopedia of Physical Science and Technology 3rd Molecular Biology

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Encyclopedia of Physical Science and Technology EN004L-956 June 9, 2001 21:7

598 DNA Testing in Forensic Science

FIGURE 6 The PCR process. Courtesy of PE Cetus Instruments. (From Schanfield, M. S. (2000). Deoxyribonucleic
Acid/Polymerase Chain Reaction. In “Encyclopedia of Forensic Sciences” (Siegel, J. A., Saukko, P. J., and Knupfer,
G. C., eds.), Academic Press, London, p. 517.)

to be detected. This is a suggested method to verify if the D8S1179, D13S317, D16S539, D18S51, D21S11, FGA,
PCR amplification was successful and that there is a PCR THO1, TPOX, and VWA03. These loci overlapped with
product to detect. the Forensic Science Services multiplexes and the Interpol
multiplexes. The 13 loci can be obtained in two amplifica-
tions using Profiler Plus and Cofiler or in a single ampli-
V. STRs USED FORENSICALLY
fication using a kit in development called Identifiler from
At this point in time with the large number of STR loci, a
1 and Powerplex 2 from Promega (Table II), or in a single
demand for a standardized panel in the United States, and
reaction with Powerplex 16 by Promega.
a need for there to be at least some sharing of loci with
forensic counterparts in Canada, England, and Europe,
A. Fluorescent Dyes
the Technical Working Group on DNA Analysis Methods
(TWGDAM) implemented a multi-laboratory evaluation Before discussing the equipment used to detect fluorescent
of those STR loci available in kits in the United States. The STRs some understanding of fluorescent dyes are neces-
loci chosen would be the PCR-based core of a national sex sary. Fluorescent dyes or minerals when subjected to light
offender file required under the 1994 DNA Identification at one wave length, such as untraviolet light or black light,
Act. The national program is called Combined DNA In- will give off colored light at a slightly different wavelength
dexing System or CODIS for short. or color. A characteristic of fluorescent dyes or materials
The TWGDAM/CODIS loci were announced at the is that the compound is excited at one frequency of light,
Promega DNA Identification Symposium in the fall of referred to as its absorption or excitation peak, and emits
1997 and at the American Academy of Forensic Sci- or gives off light a different frequency, referred to as its
ence meeting in February 1998. The following loci were emission peak.
chosen to be part of what was originally called the To label a PCR primer with a fluorescent dye, the dye

CODIS 13 loci: CSF1PO, D3S1358, D5S818, D7S820, is attached to the 5 end of the molecule. Since DNA is