copyright 1994-2000 genelex corporation forensic dna analysis forensic testing (criminal) ~25,000...
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Copyright 1994-2000
Genelex Corporation
Forensic DNA AnalysisForensic DNA Analysis
• Forensic testing (Criminal)~25,000 cases per year75% in sexual assault
• Paternity testing (Civil)220,000 cases per year
• Offender Profiling>500,000 total profiles completed
Copyright 1994-2000
Genelex Corporation
DNA Identification ApplicationsDNA Identification Applications
• Sexual assault
• Homicide and other violent crimes
• Exculpate wrongly accused suspects
• Identify serial crimes
• Identify human remains
• Sex offender tracking
Copyright 1994-2000
Genelex Corporation
Comparison of Comparison of Forensic DNA Analysis MethodsForensic DNA Analysis Methods
Discrimination Positive DQA ~ 1/8-1/50 Ability Identification Polymarker ~ 1/1000
STRs 1/10,000,000
Application Most cases Insufficient DNA for RFLP analysis
Turnaround 4-8 weeks 2-3 days
RFLP PCR
Copyright 1994-2000
Genelex Corporation
DNA Evidence SourcesDNA Evidence Sources
• Semen– Vaginal swabs -- Condoms – Undergarments -- Sheets, pillows, blankets
• Blood– Stains -- Whole blood– Backspatter -- Autopsy Tissues
• Other– Saliva -- Hair roots– Cigarette butts -- Other tissues– Envelope flaps
Copyright 1994-2000
Genelex Corporation
DNA Parentage Testing ApplicationsDNA Parentage Testing Applications
• Child support enforcement
• Kinship and sibship analysis
• Criminal paternity
• Identify human remains - reverse paternity
• Twin zygosity
Copyright 1994-2000
Genelex Corporation
DNA Parentage Evidence SourcesDNA Parentage Evidence Sources
• Paternity– Buccal (cheek) swabs– Blood and blood stains– Abortus (within 6 to 8 weeks)– Prenatal samples - CVS and amniocytes
• Post-mortem Identification– Bone, teeth, heart, brain
Copyright 1994-2000
Genelex Corporation
Preservation of EvidencePreservation of Evidence
• Air dry (no heat) all stains and swabs
• Store frozen in paper bags, not plastic
• Tissues...store frozen, preferably without preservatives
• Liquid blood...refrigerate up to a few weeks (longer term, freeze stains for DNA testing)
Copyright 1994-2000
Genelex Corporation
Environmental Effects on RFLP TestsEnvironmental Effects on RFLP Tests
Conditions• Sunlight, moderate temp.• Hot, humid weather• No sunlight, hot weather• Gas, oil, detergent, acid,
base, salt, bleach, non-human DNA
• Soil
Can Be Tested-Up to 6 weeks
-10 days or less-5 months or more-No effect
-Precludes test
Copyright 1994-2000
Genelex Corporation
Information StorageInformation Storage
Copyright 1994-2000
Genelex Corporation
Organization of InformationOrganization of Information
Volumes in a Set of Encyclopedias
23 Pairs ofChromosomes in a Cell
Printed Genetic
1 2 3 4 5 6
Copyright 1994-2000
Genelex Corporation
Identification of InformationIdentification of Information
Printed Information
Volume, Page, Line No.
Genetic Information
Chromosome, Locus
D2S44 D439S1
Copyright 1994-2000
Genelex Corporation
FertilizationFertilization
Father’s Sperm Mother’s Egg
Child’s Cell
Copyright 1994-2000
Genelex Corporation
Characteristics of DNACharacteristics of DNA
• Each person has a unique DNA profile.
• Each person's DNA is the same in every cell.
• An individual’s DNA profile remains the same throughout life.
• Most DNA is the same from person to person.
• Some DNA varies from person to person.
Copyright 1994-2000
Genelex Corporation
Father: DNA is a long, long, long, long molecule that is tightly wound.
Mother: DNA is a long, long molecule that is tightly wound.
Molecular “Scissors” (Restriction Enzyme)
Variable DNA SectionsVariable DNA Sections
Copyright 1994-2000
Genelex Corporation
Variation in the DQA GeneVariation in the DQA Gene
1.1 Therr are six versions of the DQA gene1.2 Theee are six versions of the DQA gene1.3 Ttere are six versions of the DQA gene2.0 There are six bersions of the DQA gene3.0 There are six versions of the DQA jene4.0 There are sis versions of the DQA gene
Copyright 1994-2000
Genelex Corporation
Size Separation of DNA by Gel ElectrophoresisSize Separation of DNA by Gel Electrophoresis
Total DNA
cut withrestrictionenzyme
Total DNA
Suspect Evidence Victim
-
+
Copyright 1994-2000
Genelex Corporation
Southern BlottingSouthern Blotting
DNA extracted
Restrictionenzymeproduces fragments
Double-strandedfragmentsseparated byelectrophoresis
Transfer from gel to membrane
Radioactivelylabeled probein single strand form
Develop film,DNAtypingpattern appears
Visualizebandingby exposureto X-ray film
Wash toremoveexcessprobe
Denatured to single stranded fragments
Cover membrane with probe, incubate
The Basis of RFLP Analysis
Copyright 1994-2000
Genelex Corporation
Comparative Inclusion Rates for PaternityComparative Inclusion Rates for Paternity
Verbal Predicates, according to Joint AMA-ABA guidelinesFamily Law Quarterly, Vo. X, 3, 1976.
20 95% 5%
50 98% 1-2% Very Likely
100 99% < 0.1% Extremely likely
500 99.8% ~ 0 Practically proven
Paternity Probability False Verbal Predicates Index of Paternity Positives
Copyright 1994-2000
Genelex Corporation
Matching Using a Matching Using a 2.5% Match Window2.5% Match Window
5%5%MaximumMaximumDifferenceDifference
10251025
10001000 Band ABand A
975975984984
960960 Band BBand B
936936
923923
900900 Band CBand C
878878
Copyright 1994-2000
Genelex Corporation
Binning Population DataBinning Population Data
Actual Allele FrequenciesActual Allele FrequenciesBin Bin BoundariesBoundaries
BinBinBoundariesBoundaries
BinBinFrequencyFrequency
1.0%1.0%
AA2.5%2.5%
BB4.0%4.0%
CC1.5%1.5%
DD
A + B + C + D = 9.0%
9 %Total
Copyright 1994-2000
Genelex Corporation
Calculating a DNA Profile FrequencyCalculating a DNA Profile FrequencyBand Bin Locus Combined
Locus Frequencies Frequency FrequencyBand 1 / Band 2
1 0.08 / 0.02 0.003 or ----
(8%) (2%) 1 in 333
2 0.15 / 0.04 0.012 or 1 in 28 thousand
1 in 83
3 0.08 / 0.06 0.010 or 1 in 3 million
1 in 100
4 0.22 / 0.09 0.040 or 1 in 70 million1 in 25
Copyright 1994-2000
Genelex Corporation
Forensic Quality Assurance ProgramsForensic Quality Assurance Programs
• Lab inspection and accreditation– ASCLD-LAB– AABB Parentage Testing Committee
• Personnel qualifications, training and certification– ABC-general knowledge– Specialties-DNA/serology
• Proficiency testing– College of American Pathologists, Others