DNA was extracted from blood samples by salting out. Sequenom MassArray iPLEX technology was used for SNP genotyping. PCR primers, extension primers, and multiplexing capabilities were determined with Sequenom MassARRAY Assay Designer software v3.1.2.2. Standard procedures were used to amplify PCR products; unincorporated nucleotides were deactivated with shrimp alkaline phosphatase. A single base pair extension step was completed with the mass extension primer and the terminator (iPLEX). The primer extension products were cleaned with resin and spotted onto a silicon SpectroChip. The chip was scanned with a mass spectrometry workstation (Bruker). The resulting genotype spectra were analyzed with Sequenom SpectroTYPER software v3.4.
