Chapter 20: Single-nucleotide Polymorphism Profiling

 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 Li2

 Advantages:  SNPs are abundant and can be used as markers  SNP amplicon sizes are smaller than STR ▪ bp in length  Low mutation rates ▪ Good for paternity  Many methods available ▪ Multiplex systems Forensic Biology by Richard Li3

 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 Li4

 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 Li5

 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 Li6

 Forensic identification  Paternity  Ethnic origin  Phenotyping  Nonsynonymous SNPs  Can reveal physical characteristics (e.g. eye color) Forensic Biology by Richard Li7

 Victim identification & Sexual assault cases  Amelogenin (AMEL) marker used  AMELX & AMELY  AMELY null mutations Forensic Biology by Richard Li8