Throughout the C. elegans sequencing project Genefinder was the primary protein-coding gene prediction program. These initial predictions were manually reviewed by curators as part of a "first-pass annotation" and are actively curated by WormBase staff using a variety of data and information. In the WormBase data release WS133 there are 22,227 protein-coding gene, including 2,575 alternatively-spliced forms. Twenty-eight percent of these have every base of every exon confirmed by transcription evidence while an additional 51% have some bases confirmed. Most of the genes are relatively small covering a genomic region of about 3 kb. The average gene contains 6.4 coding exons accounting for about 26% of the genome. Most exons are small and separated by small introns. The median size of exons is 123 bases, while the most common size for introns is 47 bases. Protein-coding genes are denser on the autosomes than on chromosome X, and denser in the central region of the autosomes than on the arms. There are only 561 annotated pseudogenes but estimates but several estimates put this much higher.