Forensic DNA Typing Jiang Qiang Department of Forensic

Forensic DNA Typing Jiang Qiang Department of Forensic Medicine

Outline 1. Introduction 2. Application of forensic DNA typing 3. Process of forensic DNA typing 4. Conclusion

Brief History of Forensic DNA Typing • 1980 - Ray White describes first polymorphic RFLP marker • 1985 - Alec Jeffreys discovers multilocus VNTR probes • 1985 - first paper on PCR • 1991 - first STR paper • 1995 - UK DNA database • 1998 – US CODIS database • 2000 – Other countries database • DNA parting standardization

Examples of DNA in the News 2004 Indian Ocean Tsunami 2001 “ 911”, New York 2008 Wenchuan Earthquake

What are we doing Identification Paternity testing

How to do • DNA analysis • STR, Y-STR, X-STR • mt. DNA, SNP

Methods for Human Identification Fingerprints have been used since 1901 DNA Fingerprints since 1985

Applications for Forensic DNA Typing Forensic cases - matching suspect with evidence Paternity testing - identifying father Historical investigations Missing persons investigations Mass disasters - putting pieces back together DNA database

Two main tasks of Forensic Biology Individual Identification Paternity Testing

Basic Concepts Polymerase Chain Reaction (PCR) Locus Allele STR Homozygote Heterozygote

DNA in the Cell chromosome cell nucleus Double stranded DNA molecule Individual nucleotides

principle Father’s Sperm Mother’s Egg Child’s Cell For each inherited characteristic, an organism has two genes, one from each parent. We call these genes alleles.

Short Tandem Repeats (STRs) number of repeat units Fluorescent dye label AATG Fluorescent dye creates a labeled PCR product primer 1 7 repeats 8 repeats primer 2 Locus is the region of the genome being examined Homozygote: Alleles are identical on each chromosome； both alleles are the same length Heterozygote: Alleles differ on each chromosome ； alleles differ and can be resolved from one another

Sources of Biological Evidence Blood/Blood stain Semen/ Semen stain Saliva/Saliva stain Urine Hair Teeth Bone Tissue Blood stain Only a very small amount of sample is needed to obtain a DNA profile

Forensic STR Markers on Human Chromosomes 13 CODIS Core STR Loci TPOX D 3 S 1358 D 8 S 1179 D 5 S 818 FGA CSF 1 PO TH 01 VWA D 7 S 820 AMEL Sex-typing D 13 S 317 D 16 S 539 D 18 S 51 D 21 S 11 AMEL

Steps in Forensic DNA Typing Sample Obtained from Crime Scene or Paternity Investigation Biology DNA Quantitation DNA Extraction PCR Amplification of Multiple STR markers Technology Separation and Detection of PCR Products (STR Alleles) Sample Genotype Determination Genetics Comparison of Sample Genotype to Other Sample Results If match occurs, comparison of DNA profile to population databases Generation of Case Report with Probability of Random Match

Polymerase Chain Reaction (PCR) 5’ 3’ 3’ 3’ 5’ 5’ Starting DNA Template Separate strands (denature) Forward primer 5’ 3’ Make copies (extend primers) 5’ Add primers (anneal) 3’ 3’ 5’ Reverse primer PCR is a method of amplifying a specific region of the genome – go from 1 to over a billion copies in about several hours

Multiplex PCR • Over 10 Markers Can Be Copied at Once • Sensitivities to levels less than 1 ng of DNA • Ability to Handle Mixtures and Degraded Samples • Different Fluorescent Dyes Used to Distinguish STR Alleles with Overlapping Size Ranges

Information is tied together with multiplex PCR and data analysis Amp. Fl. STR® Identifiler™ (Applied Biosystems) D 8 S 1179 D 3 S 1358 TH 01 VWA D 19 S 433 AMEL D 21 S 11 D 5 S 818 D 7 S 820 D 13 S 317 TPOX CSF 1 PO D 16 S 539 D 2 S 1338 D 18 S 51 FGA 1 integrated analysis vs. 16 separate runs

Capillary Electrophoresis Instrumentation ABI 310 single capillary ABI 3100 16 capillary array

Genetic Inheritance Pattern of DNA Profiles DAD CHILD MOM

PATERNITY TESTING Family Inheritance of STR Alleles (D 13 S 317) PCR product size (bp) Results of DNA Tests Impact Families 11 14 12 8 14 11 12 8 14 12 Father Me Child #1 Child #2 Child #3 Mother

PATERNITY TESTING Family Inheritance of STR Alleles (D 13 S 317) PCR product size (bp) 11 14 12 8 14 11 12 8 14 12 Father Me Amanda Child #1 Child Marshall #2 Child Katy#3 Mother My Wife

Crime Scene - Two Suspects Suspect 1 Suspect 2 Evidence S 1 S 2 E D 3 14, 15 15, 18 v. WA 17, 18 17, 19 FGA 23, 24 23. 2, 24

Conclusion Main Tasks Individual Identification Paternity Testing

Forensic DNA Typing The genome of each individual is unique (with the exception of identical twins) Probe subsets of genetic variation in order to differentiate between individuals DNA typing must be done efficiently and reproducibly (information must hold up in court)

Reference • Forensic DNA Typing， John Butler • NIST website: http: //www. cstl. nist. gov/biotech/strbase STRBase

谢谢各位同学! Thank you for your attention!