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The prospect for more than 13 commonly used STR Tetranucleodide loci in forensic settings Carrie Rowland Forensic Bioinformatic Services, Inc. Dayton,

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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:

1 The prospect for more than 13 commonly used STR Tetranucleodide loci in forensic settings Carrie Rowland Forensic Bioinformatic Services, Inc. Dayton, Ohio

2 An Overview: Where are we going History of DNA testing Generations of DNA tests and how performed Current methodology New prospects Conclusions

3 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.

4 Brief History of Forensic DNA Typing Ray White describes first polymorphic RFLP marker Alec Jeffreys proposes multilocus VNTR probes be used forensically first paper on PCR FBI starts DNA casework first STR paper FSS starts UK DNA database FBI launches CODIS database

5 Three generations of DNA testing DQ-alpha TEST STRIP Allele = BLUE DOT RFLP AUTORAD Allele = BAND Automated STR ELECTROPHEROGRAM Allele = PEAK

6 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

7 RFLP technology What we would like for them to look like.

8 What they often look like. Incomplete digest

9 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

10 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

11 13 CODIS Core STR Loci with Chromosomal Positions CSF1PO D5S818 D21S11 TH01 TPOX D13S317 D7S820 D16S539D18S51 D8S1179 D3S1358 FGA VWA AMEL

12 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

13 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

14 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

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16 STR alleles with n+4 stutter products D21S11 D18S51 D8S1179 DNA Size (bp) 6.3%6.2% 5.4% Relative Fluorescence Units

17 Schematic of Stutter Product Formation Process Walsh et al (1996) Nucleic Acids Res. 24: Slipped Strand Mispairing Model Normal STR Allele Replication Repeat unit bulges out when strand breathing occurs

18 Mechanism behind n+4 stutter Walsh, et al. (1996) Nucleic Acids Research 24(14):2807 DNA polymerase Template DNA

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20 What is on the horizon ? th …….locus 2. Pentanucleotide repeats 3.Mitochondrial DNA 4.Single nucleotide polymorphisms (SNPs)


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