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Copyright 1994-2000 Genelex Corporation Forensic DNA Analysis Forensic testing (Criminal) ~25,000 cases per year 75% in sexual assault Paternity testing.

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Presentation on theme: "Copyright 1994-2000 Genelex Corporation Forensic DNA Analysis Forensic testing (Criminal) ~25,000 cases per year 75% in sexual assault Paternity testing."— Presentation transcript:

1 Copyright 1994-2000 Genelex Corporation Forensic DNA Analysis Forensic testing (Criminal) ~25,000 cases per year 75% in sexual assault Paternity testing (Civil) 220,000 cases per year Offender Profiling >500,000 total profiles completed

2 Copyright 1994-2000 Genelex Corporation DNA Identification Applications Sexual assault Homicide and other violent crimes Exculpate wrongly accused suspects Identify serial crimes Identify human remains Sex offender tracking

3 Copyright 1994-2000 Genelex Corporation Comparison of Forensic 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

4 Copyright 1994-2000 Genelex Corporation DNA 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

5 Copyright 1994-2000 Genelex Corporation DNA Parentage Testing Applications Child support enforcement Kinship and sibship analysis Criminal paternity Identify human remains - reverse paternity Twin zygosity

6 Copyright 1994-2000 Genelex Corporation DNA 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

7 Copyright 1994-2000 Genelex Corporation Preservation 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)

8 Copyright 1994-2000 Genelex Corporation Environmental 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

9 Copyright 1994-2000 Genelex Corporation Information Storage

10 Copyright 1994-2000 Genelex Corporation Organization of Information Volumes in a Set of Encyclopedias 23 Pairs of Chromosomes in a Cell Printed Genetic 1 2 3 4 5 6

11 Copyright 1994-2000 Genelex Corporation Identification of Information Printed Information Volume, Page, Line No. Genetic Information Chromosome, Locus D2S44D439S1

12 Copyright 1994-2000 Genelex Corporation Fertilization Fathers Sperm Mothers Egg Childs Cell

13 Copyright 1994-2000 Genelex Corporation Characteristics of DNA Each person has a unique DNA profile. Each person's DNA is the same in every cell. An individuals DNA profile remains the same throughout life. Most DNA is the same from person to person. Some DNA varies from person to person.

14 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 Sections

15 Copyright 1994-2000 Genelex Corporation Variation in the DQA Gene 1.1 Therr are six versions of the DQA gene 1.2 Theee are six versions of the DQA gene 1.3 Ttere are six versions of the DQA gene 2.0 There are six bersions of the DQA gene 3.0 There are six versions of the DQA jene 4.0 There are sis versions of the DQA gene

16 Copyright 1994-2000 Genelex Corporation Size Separation of DNA by Gel Electrophoresis Total DNA cut with restriction enzyme Total DNA Suspect Evidence Victim - +

17 Copyright 1994-2000 Genelex Corporation Southern Blotting Southern Blotting DNA extracted Restriction enzyme produces fragments Double-stranded fragments separated by electrophoresis Transfer from gel to membrane Radioactively labeled probe in single strand form Develop film, DNA typing pattern appears Visualize banding by exposure to X-ray film Wash to remove excess probe Denatured to single stranded fragments Cover membrane with probe, incubate The Basis of RFLP Analysis

18 Copyright 1994-2000 Genelex Corporation Comparative Inclusion Rates for Paternity Verbal Predicates, according to Joint AMA-ABA guidelines Family 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

19 Copyright 1994-2000 Genelex Corporation Matching Using a 2.5% Match Window 5% Maximum Difference 1025 1000 Band A 975 984 960 Band B 936 923 900 Band C 878

20 Copyright 1994-2000 Genelex Corporation Binning Population Data Actual Allele Frequencies BinBoundariesBinBoundariesBinFrequency 1.0% A 2.5% B 4.0% C 1.5% D A + B + C + D = 9.0% 9 % Total

21 Copyright 1994-2000 Genelex Corporation Calculating a DNA Profile Frequency Band BinLocusCombined LocusFrequenciesFrequency Band 1 / Band 2 10.08 / 0.020.003 or---- (8%) (2%)1 in 333 20.15 / 0.040.012 or1 in 28 thousand 1 in 83 30.08 / 0.060.010 or1 in 3 million 1 in 100 40.22 / 0.090.040 or1 in 70 million 1 in 25

22 Copyright 1994-2000 Genelex Corporation Forensic 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


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