Forensic Biology by Richard Li

1. Chapter 19: Y-STR Profiling and Gender Typing Forensic Biologyby Richard Li

2. Basics • Y chromosome inherited by the father • Unique to males • Y-STR • Sexual assault investigations w/ male suspects • Mixtures • Number of perpetrators • Paternal lineage can be est. • Missing person cases Forensic Biology by Richard Li

3. Basics • Disadvantages of Y-STR • Discriminating power are low • Product rule does not apply • Cannot distinguish individuals with the same paternal lineage Forensic Biology by Richard Li

4. Human Y Chromosome Genome • 60 million base pairs • Two regions: • Psuedo-Autosomal Region (PAR) • Male Specific Region Y (MSY) • Repetitive elements: • STRs • Alu • LINE • SNPs Forensic Biology by Richard Li

5. Y-STR Profiling • 400 STR loci have been identified • Majority on long arm (60%) • 22% on short arm • Core repeat sizes: • 9% dimeric, 39% trimeric, 45% tetrameric, 9% pentameric, 1% hexameric • Haplotype- collection of alleles that are linked Forensic Biology by Richard Li

6. Core Y-STR Loci • European Minimal Haplotype (EMH) • 1997 • Core set of nine loci • DYS19, DYS385a/b, DYS389I, DYS389II, DYS390, DYS391, DY5392, DY5393 • U.S. Haplotype • 2003 • SWGDAM • EMH set plus tow additional loci: DYS438 & DYS439 Forensic Biology by Richard Li

7. Multiplex Y-STR Systems • Y-STR in forensic casework started in Europe • Office of Chief Medical Examiner in NYC • Facilitated by commercially available kits • Y-PLEX 6 Forensic Biology by Richard Li

8. Gender Typing • Victim identification & Sexual assault cases • Amelogenin (AMEL) marker used • AMELX & AMELY • AMELY null mutations Forensic Biology by Richard Li