The Internal Validation and Casework Application of MiniSTR Systems
Eugene Lyle Kleyn · University of the Western Cape Electronic Theses and Dissertations Repository (University of the Western Cape) · 2008
The objective of the study was to conduct an internal validation on miniSTR systems and apply it to cases received from the South African Missing Persons Task Team (SAMPTT).This was prompted by the fact that miniSTR systems have been shown to out perform some of the commercial kits available in the time of the study and provide an alternative to mtDNA when analysing degraded DNA from skeletal remains and that the DNA extracted from skeletal remains received from the SAMPTT would be degraded due to the remains generally being fragmented or charred and buried for many years.The miniSTR loci chosen for validation comprised the Combined DNA Index System (CODIS) thirteen core loci and were arranged into four triplexes and one uniplex.The internal validation studies included the following: a reaction volume study, sensitivity study, cycle number study, reproducibility and precision studies, environmental and matrix studies, mixture studies and concordance studies.Miniplex 1 and 2 exhibited sensitivity down to 100pg of DNA in 10μL reactions at 38 cycles while Miniplex 3 and 4 exhibited sensitivity down to 100pg at 33 cycles.The average allele size standard deviation ranged from 0.045-0.158bases and concordance was observed in 99% of all allele calls made.The casework received from the SAMPTT involved six bone specimens, four highly fragmented and charred 20 year old bone specimens, a 25 year old bone specimen and a 44 year old bone specimen.The miniSTR systems produced four full CODIS profiles and two partial CODIS profiles for the bone specimens.This enabled the identities of four of the six bone specimens to be resolved.To support the miniSTR results and resolve the other cases, mtDNA and Y-STR typing were utilised.The DNA analysis data augmented the non-DNA evidence supporting the hypothesis that the bone specimens were derived from ANC activists who were abducted, tortured and murdered by the South African Security Police during the period 1963-1987.