Forensic Biology by Richard Li

1. Chapter 20: Single-nucleotide Polymorphism Profiling Forensic Biologyby Richard Li

2. Basic Characteristics of SNPs • Variations in the human genome • Single-base pair change originating from spontaneous mutations • Majority of human DNA polymorphisms • 1.4 million identified • Most are bi-allelic Forensic Biology by Richard Li

3. Basic Characteristics of SNPs • Advantages: • SNPs are abundant and can be used as markers • SNP amplicon sizes are smaller than STR • 50-100 bp in length • Low mutation rates • Good for paternity • Many methods available • Multiplex systems Forensic Biology by Richard Li

4. Basic Characteristics of SNPs • Disadvantages: • SNPs are not as polymorphic • Difficult to resolve mixed profiles • Majority of DNA databases contain STR profiles instead of SNP Forensic Biology by Richard Li

5. Forensic Applications • First use was with sequence polymorphisms at the HLA-DQA1 locus • Commercial kits: • DQα AmpliType Kit • AmpliType PM PCR amplification and Typing kit Forensic Biology by Richard Li

6. Forensic Applications • Allele-specific oligonucleotide hybridization assays • Analyzes single nucleotide variations at a given locus • ASO probes hybridize to its complementary DNA sequences in question to distinguish known polymorphic alleles • PCR based Forensic Biology by Richard Li

7. Recent and Potential Applications • Forensic identification • Paternity • Ethnic origin • Phenotyping • Nonsynonymous SNPs • Can reveal physical characteristics (e.g. eye color) 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