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STRmix™ EMPOWERING FORENSIC SCIENCE

How

How does FaSTR™ DNA work?

DNA analysis is a process of identifying alleles. The alleles appear as peaks in an electropherogram (EPG) and are identified from their locations within the EPG. The locations are determined using internal size standards and allelic ‘ladders’.

FaSTR™ DNA

Contains the size-standard and allelic ladder data for commonly-available multiplex profiling kits. Additional kits and size standards can easily be added by importing panel, bin, and size standard information, or by manual entry.

Based on an adaptation of the fundamental process implemented in OSIRIS[1], FaSTR™ DNA applies a set of fully configurable rules to identify and label alleles and reject artefacts within the EPGs of samples.

The Analysis Process

Raw data are produced by capillary electrophoresis instruments and written in the form of .fsa, .hid or .promega data files. FaSTR™ DNA analyses raw DNA profile data by:

  1. Smoothing and dynamic baselining of the raw data.
  2. Detection and assignment of size standard peaks for the accurate sizing of peaks in the allelic ladder(s) and sample(s).
  3. Size alignment of peaks detected in the allelic ladder(s) with peaks detected in the sample(s) to apply allele calls.
  4. Optionally applying a set of analysis rules to distinguish artefactual from allelic peaks.
  5. Optionally undertaking NoC estimation for autosomal[2] or Y-STR profiles.
  6. Optionally undertaking sample to sample or sample to database comparison checks.
  7. Undertaking full concordance testing on positive and negative controls, including quality marker and primer flare quality checks.
  8. Exporting the results in various configurable formats.
  9. Optionally undertaking a project review to compare two analysed projects and resolve conflicts to create a final reviewed project.

 

Outputs

FaSTR™ DNA displays the results of its analysis (the ‘DNA profile’), as a labelled EPG and as a table of locus and peak designations.  With FaSTR™ DNA you can:

  • Easily print EPGs and include snapshots of areas of interest.
  • Easily print a report of changes made to peaks during analysis.
  • Export analysed data to STRmix™, the supplied FaSTR™ DNA CODIS tool or a genotype table.
  • Save the analysis as a ‘project’ (.fpj) for future reference.

Configuration parameters

The analysis settings can be general or specific to each profiling kit type and locus. FaSTR™ DNA contains easily customisable default kits and methods. You can also create (and save) customised sets of parameters appropriate to different types of DNA samples (e.g. known reference and crime-scene samples).

 [1]  R.M. Goor, L. Forman Neall, D. Hoffman, S.T. Sherry, Mathematical approach to analysis of multiplex DNA profiles, Bull Math Biol 73(8) (2011) 1909-1931

 [2]  M. Kruijver, H. Kelly, K. Cheng, M.-H. Lin, J. Morawiitz, L. Russell, J. Buckleton, J.A. Bright, Estimating the number of contributors to a DNA profile using decision trees, Forensic Science International: Genetics 50 (2021) 102407