Figure 1. Flowchart for GRouping and Identification of Sequence Tags (GRIST). High quality matches (HQM) under our default conditions are at least a 97% identity over a minimum length of 50 bp for NCBI RefSeq/NR (non-redundant) database matches and 96% identity over a minimum 100 bp length for NCBI dbEST database matches. Blast matches against NR are filtered to ignore multigene clones (such as bacterial artifical chromosomes [BACs]) and known artifacts. NR matches are checked for GeneID and are grouped with RefSeq matches for the same GeneID. This takes account of short or incomplete RefSeqs. Unigenes are assigned independently by BLAST against dbEST. UniGene assignments for the top eight HQM dbEST matches for each clone are identified, and those that occur at frequencies of at least 15% for the whole group are reported. This can help identify Unigene problems, overlapping genes, and variant transcripts.