Reorganization and merging of the EMBL and GenBank keyword indexes in a tree structure for more efficient retrieval of nucleic acid sequences.

EMBL and GenBank keyword indexes have no hierarchical structure. In this paper we present a method for merging and reorganizing them in a tree structure whose primary roots are the keywords 'protein', 'DNA', 'RNA', and 'unclassified'. Synonymous keywords have been grouped together and erroneous keywords have been corrected. This taxonomic organization of keywords results in a more extensive and efficient retrieval which is further aided by "synonyms declaration". The tree has been produced using the computer programs GENPOINT and CREANET.