 The majority of gene structure changes have been based on transcript data from large scale projects such as Yuji Kohara's EST libraries, Mark Vidal's Orfeome project (worfdb.dfci.harvard.edu/) Waterston and Hillier's Illumina data and Makedonka Mitreva's 454 data.However, other data types (e.g.protein alignments, "ab initio" prediction programs, trans-splice leader sites, poly-A signals and addition sites, SAGE and TEC-RED transcript tags, mass-spectroscopic peptides, and conserved protein domains) are useful in refining the structures, especially where expression is low and so transcripts are not sufficiently available.