In transcriptome approaches, probes corresponding to individual members of multigenic families often lack specificity and are responsible of molecular cross-hybridization events.
SPADS uses a strategy to optimize the selection of specific probes or GST (Gene Specific Tag) in a poor conserved region of each gene in a given genome. It can be applied when the genome considered is fully sequenced or if the gene family involved is exhaustively characterized. From a gene for which the intron-exon structure is known (or predicted), the program selects, by comparison with the whole genome, the less conserved region(s), and designs a primer pair specific to that region for its amplification from genomic DNA.

see online : Spads webpage