Familial DNA

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  • Based on the principle that family members share more of their DNA than more distantly related people
    • Familial DNA
      • Devised by the Forensic Science Service
        • Has provided 188 familial searches to police investigations (2002-2011)
          • Identified 41 offenders/suspects in serious crimes
      • Kinship Analysis
        • As DNA is inherited from our mothers and fathers, relationships can be investigated between members of the family
          • DNA markers can be used to identify 'relatedness'
            • Autosomal STRs are routinely used
              • The most discriminating
              • mitrochondrial (mtDNA) can also be used to investigate the maternal lineage
                • Less discriminating
              • STRs on the Y chromosome (Y-STRs) are used to study inheritance through the paternal line
                • Less discriminating
                • Paternity Testing
                  • A medical test, to determine whether a man may be the father of  particular child
                    • Blood test
                    • Buccal swabs
                      • Due to sensitivity of STR analysis
                  • As mutations can occur between generations, you need to have exclusions at 3 loci before a test is said to be negative
                    • If a man cannot be excluded at 3 of more loci, then we consider two hypotheses and calculate Likelihood Ratio
                      • Ascertains the significance of the result
                        • Paternity Index
                        • Punnett Square
                          • used to determine the possible genotypes
          • DNA profiling can assist in testing for possible paternity, sibling ship and other relationships
        • Limitations
          • As the genetic distance between relatives increases (half siblings), the evidential strength of kinship analysis decreases
          • reliant upon availability of close relatives
            • Are they on the database?
          • If a mutation occurs, then it may result in an apparent inconsistency with Mendelian inheritance
        • Uses
          • Incest cases
          • Paternity cases
          • Missing persons
          • Mass disasters
      • Examples
        • Golden State Killer
          • Uathorities used DNA profiles from an ancestry site to help them find matches
        • Craig Harman
          • Harman threw a brick into the car window of Michael Little. Little died of a heart attack. Blood was found on the brick and was use for familial searching.
        • Gladys Godfrey
          • Godfrey was murdered in 2002 - DNA samples were run on the NDNAD in order to find close matches
      • Identification of human remains
        • DVI
          • Often remains are unrecognisable for identification purposes
        • World Trade Center Attacks (2001)
    • Ability to use a database to identify a suspect
      • Used when there is not a full DNA profile match between the crime scene sample and NDNAD sample
        • A match is achieved at 15 or more alleles
    • Children
    • Parents
    • Siblings

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