e2g [Krüger et al. 2004] is a web-based server which efficiently maps large expressed sequence tag (EST) and cDNA datasets to genomic DNA. It significantly extends the volume of data that can be mapped in reasonable time, and makes this improved efficiency available as a web service. The server hosts large collections of EST sequences (e.g. over 4 million mouse ESTs of 1.87 GB) in precomputed indexed data structures for efficient sequence comparison.

The user can upload a genomic DNA sequence of interest and rapidly compare this to the complete collection of ESTs on the server. This delivers a mapping of the ESTs on the genomic DNA, allowing users to

• rapidly detect new genes
• verify the exon-intron structure of predicted genes
• determine splice variants in the uploaded genomic region of interest

The e2g webinterface provides a graphical overview of the mapping. Alignments of the mapped EST regions with parts of the genomic sequence are visualized. Zooming functions allow the user to interactively explore the results. Mapped sequences can be downloaded for further analysis.