Table 1.

Genes, exons and introns in yeast, rice and humans

	Yeast	Rice	Humans
Total genes	6,000	50,000-60,000	25,000-40,000
Intronless genes	＞5,700	11,109	6,227
Percentage of intronless genes	95%	∼20%	∼20%
Average internal exon size	N/A	300 bp-500 bp	140 bp-180 bp
Average numbers of exons	＜2	4-5	8-10
Alternative splicing of multiple-exon genes	Rare	＞50%	＞95%
Splicing mechanism	Spliceosome mediated	Intron definition	Exon definition
Average intron size	＜200 bp	300 bp-550 bp	3,500 bp-5,500 bp

Based on previous publications (8, 23, 38, 54-57) and MSU Rice Genome Annotation, Release (http://rice.plantbiology.msu.edu/analyses_facts.shtml).