Number of Arabidopsis thaliana probe-pairs and probe-sets from the ATH1-121501 GeneChip® array used to study the transcriptome of Brassica oleracea var. alboglabra cv. A12DHd as a function of the gDNA hybridisation intensity thresholds used to generate the probe mask files. Filled circles are scaled to the left-hand y-axis (i.e. probe-sets used in probe mask files) and unfilled circles are scaled to the right-hand y-axis (i.e. probe-pairs used in probe mask files). Data were obtained by hybridising genomic DNA from B. oleracea to the A. thaliana ATH1-121501 GeneChip® array.