Botany of this species is encoded by about 135 million base pairs of DNA, forming one of the smallest genomes among flowering plants. "Arabidopsis" was the first plant to have its genome sequenced, in 2000. The sequencing of some other relatively small genomes, of rice ("Oryza sativa") and "Brachypodium distachyon", has made them important model species for understanding the genetics, cellular and molecular biology of cereals, grasses and monocots generally. Model plants such as "Arabidopsis thaliana" are used for studying the molecular biology of plant cells and the chloroplast. Ideally, these organisms have small genomes that are well known or completely
Rissoina oryza Rissoina oryza Rissoina oryza is a species of minute sea snail, a marine gastropod mollusk or micromollusk in the family Rissoinidae. The height of the small, white shell attains 2 mm. The shell has an oblong-ovate shape. It is solid, smooth, and shining, The spire is moderately elevated, and rather rapidly tapering. The apex is obtuse. The 6-7 whorls are flatly convex. The body whoprl is rather large, and slightly compressed beneath. The suture is faintly impressed and broadly margined beneath. The rather large aperture is oblique and has a sub-ovate shape. The thick peristome is dilated. The columella is