 Directed evolution has been employed to generate a FokI variant with enhanced cleavage activity that the authors dubbed "Sharkey".Structure-based design has also been employed to improve the cleavage specificity of FokI by modifying the dimerization interface so that only the intended heterodimeric species are active.Zinc finger nucleases are useful to manipulate the genomes of many plants and animals including arabidopsis, tobacco, soybean, corn, "Drosophila melanogaster", "C. elegans", "Platynereis dumerilii", sea urchin, 
silkworm, 
zebrafish, frogs, mice, rats, rabbits, pigs, cattle, and 
various types of mammalian cells.