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STR Data Analysis and Interpretation for Forensic Analysts


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National Institute of Justice (NIJ) (see reuse policy).

Genotyper® converts GeneScan® sized peaks into genotype calls using predefined macros, providing defined results. Genotyper® uses the tabular data from GeneScan® to make allele calls using the first ladder recognized by the program. The two main manufacturer macros for the proprietary kits are Kazam for analysis of AmpFℓSTR® amplification kits and PowerTyper™ for Promega products.

These macros do three things:

  • Calculate the bin offsets (alleles) based on the tabular data for sizing
  • Filter stutter as defined in the macro
  • Assign the number(s) that represent the genotypes for the profile (based on the ladder used for the sample set)

The macro is simply a step list of actions that are performed sequentially as defined when a particular template is launched. Macros are used to check the size standard by attaching the labeled sizes for confirmation; others can be written to label peaks and to set up Genotyper® tables. After assignment of allele labels, the analyst proceeds with the interpretation of the overall profile.

Below is a screen shot of Genotyper®, focusing on the macro window. Click on the macro labeled "Kazam" to view the steps of the macro as they appear in text format.

Genotyper® macro window
National Institute of Justice (NIJ) (see reuse policy).

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