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The FBI DNA Laboratory: A Review of Protocol and Practice Vulnerabilities
May 2004
Office of the Inspector General
Appendix I
As noted in Chapter Two, Section I.D, the primers used during the amplification process contain different fluorescent labels, which allow the lasers in the capillary electrophoresis machine to detect and differentiate the various DNA fragments separated during capillary electrophoresis. The label on each primer determines the color in which the results are displayed on both computer monitors and printouts. At the present time, the fluorescent labels produce peaks that are blue, green, and yellow. The yellow peaks are usually displayed in black on the Genescan® and Genotyper® printouts, with the remaining peaks printed in the corresponding color. In addition, the internal lane standard peaks are always displayed in red.
At the present time, two amplification kits1 are required for forensic scientists to test the 13 chromosomal locations that comprise a DNA profile. Scientists also test a 14th location, known as amelogenin, which indicates the sex of the DNA contributor. One amplification kit, Profiler Plus,™ contains the reagents necessary to test ten chromosomal locations. The fluorescent labels in this kit produce results that are shown in blue for three chromosomal locations, four locations are shown in green, and three locations are called yellow even though they display in black. The COfiler™ amplification kit displays the results for two chromosomal locations in blue, four locations are displayed in green, and one location representing the yellow peaks is displayed in black. Three chromosomal locations are tested with both the Profiler Plus™ and COfiler™ kits, which gives forensic scientists points of comparison to ensure the results are consistent between the two kits.
The Genescan® graphic for the positive control in Appendix 2 reflects the DNA profile of a sample used as a positive control by a CODIS participating laboratory. The following table represents the allele calls that correspond to the electrophoresis results shown in that graphic.
Example of a DNA Profile
The following pages contain the Genotyper® printouts supporting the allelic values listed in the above chart. These printouts reflect the fact that Genotyper® reformats the Genescan® data and allows the forensic scientist that reviews the data to review only the specific peaks required for data interpretation, including (but not limited to) the specific peaks from the DNA sample and the allelic ladders. The background noise is filtered out in the Genotyper® view.
[Images not available electronically]
Applied Biosystems
Analysis KitChromosomal
LocationAlleles Present in
DNA SampleGenotyper®
Printout AmpFlSTR® Profiler Plus™
PCR Amplification KitD3S1358 14, 15 Page 141 VWA 17, 18 FGA 23, 24 Amelogenin X, X Page 141 D8S1179 13, 13 D21S11 30, 30 D18S51 15, 19 D5S818 11, 11 Page 142 D13S317 11, 11 D7S820 10, 11 AmpFlSTR® COfiler™
PCR Amplification KitD3S1358 14, 15 Page 142 D16S539 11, 12 Amelogenin X, X Page 143 THO1 8, 9.3 TPOX 8, 8 CSF1PO 10, 12 D7S820 10, 11 Page 143 Genotyper® View: Profiler Ladder
with Positive Control Allele call
Footnotes