- The human GRB2 and Drosophila Drk genes can functionally replace the Caenorhabditis elegans cell signaling gene sem-5. Stern, M.J., Marengere, L.E., Daly, R.J., Lowenstein, E.J., Kokel, M., Batzer, A., Olivier, P., Pawson, T., Schlessinger, J. Mol. Biol. Cell (1993)