Presentation on theme: "The prospect for more than 13 commonly used STR Tetranucleodide loci in forensic settings Carrie Rowland Forensic Bioinformatic Services, Inc. Dayton,"— Presentation transcript:
The prospect for more than 13 commonly used STR Tetranucleodide loci in forensic settings Carrie Rowland Forensic Bioinformatic Services, Inc. Dayton, Ohio www.bioforensics.com
An Overview: Where are we going History of DNA testing Generations of DNA tests and how performed Current methodology New prospects Conclusions
Six criteria for judging a DNA profiling system 1. Discrimination power. 2. Sensitivity. 3. Absence of, or the ability to reconcile technical artifacts. 4. Speed. 5. Ability to deconvolve mixtures. 6. Amenability to database searches.
Brief History of Forensic DNA Typing 1980 - Ray White describes first polymorphic RFLP marker 1985 - Alec Jeffreys proposes multilocus VNTR probes be used forensically 1985 - first paper on PCR 1988 - FBI starts DNA casework 1991 - first STR paper 1995 - FSS starts UK DNA database 1998 - FBI launches CODIS database
Three generations of DNA testing DQ-alpha TEST STRIP Allele = BLUE DOT RFLP AUTORAD Allele = BAND Automated STR ELECTROPHEROGRAM Allele = PEAK
How do they fare? Discriminating power Sensitivity Technical artifacts Speed Mixtures Databasing Discriminating power Sensitivity Technical artifacts Speed Mixtures ٱ Databasing RFLP DQ-alpha STR Discriminating power Sensitivity Technical artifacts Speed Mixtures Databasing
RFLP technology What we would like for them to look like.
Available Kits for STR Analysis Kits make it easy for labs to just add DNA samples to a pre-made mix 13 CODIS core loci –Profiler Plus and COfiler (PE Applied Biosystems) –PowerPlex 1.1 and 2.1 (Promega Corporation) Increased power of discrimination –CTT (1994): 1 in 410 –SGM Plus (1999): 1 in 3 trillion –PowerPlex 16 (2000): 1 in 2 x 10 17
An Example Forensic STR Multiplex Kit D3FGAvWA 5-FAM (blue) D13 D5 D7 NED (yellow) AD8D21D18 JOE (green) GS500-internal lane standard ROX (red) AmpFlSTR ® Profiler Plus Kit available from PE Biosystems (Foster City, CA) 9 STRs amplified along with sex-typing marker amelogenin in a single PCR 100 bp 400 bp300 bp200 bp Size Separation Color Separation
STR Allele Frequencies Caucasians (N=427) Blacks (N=414) Hispanics (N=414) TH01 Marker * Proc. Int. Sym. Hum. ID (Promega) 1997, p. 34 Number of repeats Frequency
amelogenin D19 D3 D8 TH01 VWA D21 FGA D16 D18D2 amelogenin D19 D3 D8 TH01 VWA D21 FGA D16 D18 D2 Two different individuals DNA Size (base pairs) Results obtained in less than 5 hours with a spot of blood the size of a pinhead probability of a random match: ~1 in 3 trillion Human Identity Testing with Multiplex STRs Simultaneous Analysis of 10 STRs and Gender AmpFlSTR ® SGM Plus kit
FBIs CODIS DNA Database Combined DNA Index System Launched October 1998 Used for linking serial crimes and unsolved cases with repeat offenders Links all 50 states Requires >4 RFLP markers and/or 13 core STR markers Current backlog of > 600,000 samples As of June, 2004 Total profiles = 1,857,093 Total forensic profiles = 85,477 Total convicted offender = 1,771,616
STR alleles with n+4 stutter products D21S11 D18S51 D8S1179 DNA Size (bp) 6.3%6.2% 5.4% Relative Fluorescence Units
Schematic of Stutter Product Formation Process Walsh et al (1996) Nucleic Acids Res. 24: 2807-2812 Slipped Strand Mispairing Model 12 3 45 123456 Normal STR Allele Replication Repeat unit bulges out when strand breathing occurs
Mechanism behind n+4 stutter Walsh, et al. (1996) Nucleic Acids Research 24(14):2807 DNA polymerase Template DNA 1 2 3 4 5 6 1 2 3 4 5 6 7