Mass spectra for allele-specific expression analysis. (A) Interleukin 6 gene. Peaks are identified by C, T and S. C represents the allele where the polymorphic site has a C residue. T represents the allele where the polymorphic site has a T residue. S represents the competitor. The peak areas of C, T and S peaks are automatically computed by the RT software package (SEQUENOM). The peak area ratios represent the concentration ratios of the starting cDNA sequences and the competitor. The peak frequencies are 0.209, 0.263 and 0.528 for peak C, T and S, respectively. (B) lexA gene. Peak S, G and C represent the competitor, the exogenous and the endogenous lexA gene, respectively. Without arabinose induction, only endogenous lexA gene expression was seen. With modest arabinose induction, both the endogenous and exogenous lexA gene expression were seen. Without induction, the peak frequencies are 0.601, 0.004 and 0.395 for peak S, G and C, respectively. With induction, the peak frequencies are 0.509, 0.075 and 0.416 for peak S, G and C, respectively. (C) ABCD-1 gene. Mut and WT represent mutant and wild type alleles, respectively. For Q672X, the peak frequencies are 0.984 and 0.016 for peak Mut and WT, respectively. For S213C, the peak frequencies are 0.187 and 0.813 for peak Mut and WT, respectively. For S108W, the peak frequencies are 0.995 and 0.005 for peak WT and Mut, respectively.