Forensic DNA Testing MN BCA Forensic Science Services
DNA Testing Capabilities • Short Tandem Repeats • Autosomal testing • Y-chromosome testing • Paternal inheritance • Mitochondrial sequencing • Control region • Maternal inheritance • Databasing
Testing Results • A full autosomal DNA profile consists of 15 polymorphic loci and 1 marker that is used to determine gender. • One multiplex amplification. • The probability of a random match in the general population is less than 1 in 1015. • There is no known link between these markers and disease.
DNA Databasing • Forensic DNA samples collected from crime scene evidence • DNA samples taken from convicted offenders • Missing persons • Unidentified human remains • Close relatives • Deduced victim knowns • Toothbrush • Hairbrush
What isn’t put in a DNA Database? • Suspect profiles • Samples obtained by search warrant • Voluntary samples • Victim profiles • Elimination profiles • Husband/Boyfriend
Missing Persons • Unidentified Human Remains • Searched against Forensic, Offender, Relatives, and Deduced Victim Knowns • Close Relatives • Searched against Unidentified Human Remains and Deduced Victim Knowns • Must have signed consent form on file • Deduced Victim Knowns • Searched against Forensic, Offender, Relatives, and Deduced Victim Knowns
Mitochondrial DNA Testing • Short, circular DNA found in the cytoplasm • ~16kb in length • Control region is sequenced in two parts • HV1 and HV2 • Results are compared to reference sequence • Family relationships along the maternal line. • Was it the Tsar’s family in the well? • Missing persons
Mitochondrial DNA Testing • FBI-Cooperative agreement • Accept cases from different states • Hairs, bones, teeth, etc. • Hair shafts • New and old bones • Maternal inheritance • “DNA of last resort” • If STR’s will not/did not work
Summary • STR’s used in forensics have 4bp core repeat units. The DNA profile is determined by the number of repeats at each locus. • Databasing allows law enforcement agencies to share DNA information. • Y-Chromosome testing allows us to ignore the female components of mixtures. • Mitochondrial DNA testing can provide information from hair shafts, bones and teeth.