Application Note: Consideration for the Evaluation of Plus Stutter for AmpFℓSTR® PCR Amplification Kits in Human Identification Laboratories
6 February 2013

AmpFℓSTR® PCR Amplification kits use PCR to amplify short tandem repeat (STR) loci in multiplex assays. The STR fragments are then visualized via capillary electrophoresis on genetic analyzers. Peaks other than the desired alleles may be detected, such as stutter products. The primary mechanism for the formation of stutter products in STR sequences was first reported more than 20 years ago and offered as a theory for genetic evolution. For Human Identification analysis, understanding the characteristics of stutter peaks is particularly relevant when samples contain DNA mixtures. This article will address stutter products and the current understanding of their formation and significance in commonly used AmpFℓSTR kits.