NCJ Number
246756
Journal
Forensic Science International: Genetics Volume: 8 Issue: 1 Dated: January 2014 Pages: 213-218
Date Published
January 2014
Length
6 pages
Annotation
Increased height of stutter peaks is a phenomenon with low copy number LCN short tandem repeat STR typing that can impact interpretation.
Abstract
Increased height of stutter peaks is a phenomenon with low copy number LCN short tandem repeat STR typing that can impact interpretation. An alternative strategy of lowering the annealing/extension temperature LT at 56 degrees C was designed to attempt to decrease the heights of stutter peaks. STR typing results were generated in terms of stutter ratios using LT-PCR conditions and compared with data obtained using standard STD PCR conditions. DNA samples ranging from 100 to 25pg were amplified using reagents contained in the AmpF&STR Identifiler PCR Amplification or AmpF&STR Identifiler Plus PCR Amplification kits with 32 or 34 PCR cycles. Stutter ratios decreased by an average of 14.7%, 14.9% and 18.1% at 100, 50 and 25pg of template DNA under LT conditions compared with those of STD conditions in the Identifiler Kit amplified samples. The LT conditions also decreased average stutter ratios by 13.3% compared with those of STD conditions in the Identifiler Plus Kit amplified samples. The overall PCR efficiency obtained with STD and LT conditions with the two STR kits was comparable in terms of the number of detected alleles, peak heights and peak height ratios. These results support the hypothesis that a lower temperature annealing/extension step reduces the likelihood of slippage during PCR by enhancing the stability of the DNA polymerase/template DNA complex or the stability of the generated duplex than the conditions of the standard extension step. This stability in turn would result in lower stutter ratios.