Samples are prepared by mixing 2 ||L of the amplified sample with a 1 ||L aliquot of the CXR-labeled fluorescent internal lane standard and 3 ||L of Bromophenol blue loading solution (95% formamide, 0.05% bromophenol blue, 10 mM NaOH). This mixture is heated to 95°C for two minutes and then snap-cooled on ice to denature the DNA strands present in the sample. An aliquot of 2.5-3 | L of this sample is then loaded onto the appropriate lane of the gel (Schumm et al. 1997, Promega Corporation 1999). Allelic ladders are prepared in a similar fashion and loaded onto the gel every five or six lanes. Note that while internal lane standard 400 works to size PowerPlex 1.1 STR loci, the extra high molecular weight DNA bands in the internal lane standard 600 are needed to properly size the large alleles in Penta E and FGA STR systems.
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