Gene structure and organization in Caenorhabditis elegans.

The sequencing of the 100 Mb Caenorhabditis elegans genome-containing approximately 14,000 genes-is approximately 50% complete. One of its most interesting features is its compactness; introns and intergenic distances are unusually small and, surprisingly, approximately 25% of genes are contained in polycistronic transcription units (operons) with only approximately 100 bp between genes.