JIGSAW is a gene prediction program, which bases it's gene calls on a target genomic sequence and output from a gene structure annotation database.
Data available for download from UCSC's annotation database is used as input and includes the following tracks of evidence: Known Genes, Ensembl, RefSeq, Geneid, Genscan, SGP, Twinscan, Human mRNAs, TIGR Gene Index, UniGene, 'Most Conserved' Elements and Non-human RefSeq Genes. GlimmerHMM and Genezilla, two open source ab initio gene finding programs are also used.
Thanks to the groups whose data is used as input for making their work publicly available.