Forensic DNA Testing

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Forensic DNA Testing

• MN BCA Forensic Science Services

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DNA Testing Capabilities

• Short Tandem Repeats
• Autosomal testing
• Y-chromosome testing
• Paternal inheritance
• Mitochondrial sequencing
• Control region
• Maternal inheritance
• Databasing

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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.

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Quick ViewWhat is a DNA Profile?
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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

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What isnt put in a DNA Database?

• Suspect profiles
• Samples obtained by search warrant
• Voluntary samples
• Victim profiles
• Elimination profiles
• Husband/Boyfriend

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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

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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 Tsars family in the well?
• Missing persons

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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 STRs will not/did not work

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Summary

• STRs 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.