Genetically modified thale cress (Arabidopsis thaliana) flowers. Experimental Arabidopsis thaliana plant, which has an altered gene that gives its flowers seven petals, rather than the usual four. This plant is popular as a model organism in plant biology and genetics as it has one of the smallest plant genomes, which was the first plant genome to be sequenced. It is a popular tool for understanding the molecular biology of many plant traits, including flower development and light sensing.