Probe classes according to their position relative to an intron. The black arrow represents the coding strand of a gene. Probes are identical to the coding strand. Nucleotide numbering begins at the first nucleotide of the contig, on the coding strand of the gene of interest; x represents the numbering of the last nucleotide of the exon preceding the 5' end of the intron, and y represents the numbering of the first nucleotide following the 3' end. Probe classes are indicated by the colored boxes.