The phosphorylation of specific tyrosine residues has beenshown to be a primary mechanism of signal transduction during normalmitogenesis, cell cycle progression and oncogenic transformation, its role inother areas such as differentiation and gap junction communication, is amatter of active and ongoing research. Antibodies that specifically recognizephosphorylated tyrosine residues have proved to be invaluable to the study oftyrosine phosphorylated proteins and the biochemical pathways in which theyfunction.