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DNA Fingerprinting: UWC developments on Y-chromosome profiling

DNA Fingerprinting: UWC developments on Y-chromosome profiling. Eugenia D’Amato Research Manager Forensic DNA Lab University of the Western Cape. DNA Fingerprinting. Genetic individual profiling using highly variable DNA located in our chromosomes .

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DNA Fingerprinting: UWC developments on Y-chromosome profiling

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  1. DNA Fingerprinting:UWC developments on Y-chromosome profiling Eugenia D’Amato Research Manager Forensic DNA Lab University of the Western Cape SAASTA-March 2009

  2. DNA Fingerprinting Genetic individual profiling using highly variable DNA located in our chromosomes. DNA utilized in profiling = STR (Short Tandem Repeats or Microsatellites) Sir Alec Jeffreys SAASTA-March 2009

  3. How a genetic profile is generated The human genome is composed by 22 pair of autosomal chromosomes and 1 pair of sexual chromosomes. The 2 chromosomes of each pair in inherited from our mother and our father. Mother Father Large individual variation occurs at microsatellites. XY determines a male XX determines a female SAASTA-March 2009

  4. How a genetic profile is generated.. Non-sexual chromosomes TAGA Maternal chromosome = 4 repeats Paternal chromosome = 7 repeats Millions of copies of several DNA fragments (markers) are obtained in a single tube by the technological procedure called PCR. The products of the PCR are separated by size in automatic instrumentation. Application: individual identity, e.g. paternity analysis SAASTA-March 2009

  5. In a paternity testing: Mather Male 1 Male 2child (TAGA)3 (TAGA)4 (TAGA)7 (TAGA)8 (TAGA)10 (TAGA)14 SAASTA-March 2009

  6. Y-chromosome • Y-chromosome is a single block of DNA that is fully transmitted from fathers to sons • information in the Y-chromosome is used to define lineages • related men in the same paternal lineage share the same Y-chromosome genetic profile SAASTA-March 2009

  7. Y-chromosome STRs Forensic application: rape cases • Differential extraction of DNA from sperm • PCR targets only male DNA in excess if victim’s DNA Over 54000 cases/year are reported to SAP • 15% of reported cases result in conviction • 41% of victims are children SAASTA-March 2009

  8. Brief history of Y-STR genotyping • 1997: 9 markers, the Minimal Haplotype, are recommended for Court use • 2000: establishment of the Y-HRD at present: 72 000 profiles MH 16 000 profiles with additional 8 markers • 2004, 2006: reviews on all known Y-STRs (~400) SAASTA-March 2009

  9. Developments in forensic Y-genotyping: • International standardization of nomenclature (ISFG- NIST) • Commercial developments Promega: 12 markers (MinH + 3) Applied Biosystems: 17 markers (MinH + 8) SAASTA-March 2009

  10. Profiling – the crime scene • Is there a match? • If so, how rare is this profile?? crime scene MATCH suspect 1 victim- female suspect 2 SAASTA-March 2009

  11. How unique is a profile? To answer this question we need large amount of data Y-HRD DATABASES Promega Applied Biosystems SAASTA-March 2009

  12. FDL lab studies on Y-STR markers 2004: UWC-genetic diversity studies in local population groups Sampling : buccal swabs Approved by Ethics Committee – UWC samples are provided by unrelated volunteers who remain anonymous 2005: new Y-STR markers are discovered in the FDL SAASTA-March 2009

  13. UWC data YHRD Database SAASTA-March 2009

  14. Analysis of population diversity • Poor genetic diversity in SA low DC , Xhosa = 0.62 European DC ~ 0.75-0.85 Few profiles in high frequency 13% Xhosa share same profile Europeans ~ 5 % • Consequences: limited forensic utility of these markers Discrimination = No distinct profiles capacity No profiled individuals SAASTA-March 2009

  15. The FDL Y-STR project • Design of a new system to profiling males that is more efficient for the SA population • 1. Profiling of 3 population groups at 45 Y-STRs • 2. selection of the best markers • 3. Optimize the PCR , single reaction. SAASTA-March 2009

  16. DC of commercial systems and UWC system * Indian English * * ALL Xhosa 9 markers 12 markers 17 markers * European values SAASTA-March 2009

  17. The UWC 10-plex SAASTA-March 2009

  18. Advantages of UWC development • Higher discrimination capacity • Lower cost • Some markers provide information about population group (African - Indian) need for population data !! SAASTA-March 2009

  19. Further studies- research • Development of statistic tools simulation of Y-profiles match-P and databases Research project with Statistics Dept- UWC SAASTA-March 2009 Haplogroup Ib2 Haplogroup R1b3

  20. The way forward… • Screening of additional population groups in South Africa and Africa using • Commercial markers • UWC markers • Link-up with interested parties • Offer the service for resolution of rape cases SAASTA-March 2009

  21. Lab members Staff PostDoc Sean Davison Eugenia D’Amato Mongi Benjeddou Students Tasneem Geduld (MSc) Curtis Cole-Showers (PhD) Shafieka Isaacs (MSc) Khadija Mwema (MSc) Zainu Abrahams (MSc) Tiro Tau (MSc) Kevin Cloete (MSc) www.forensicdnalab.org.za SAASTA-March 2009

  22. THNX ! questions? SAASTA-March 2009

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