Dri has been shown to be a sequence- specific DNA binding protein. It is therefore likely that the phenotypes exhibited by dri mutant embryos result from disruption to the expression of regulatory genes.
Terminal development is disrupted in the dri maternal and zygotic mutant embryos.
Both head and tail defects are invariably observed in dri maternal and zygotic mutant embryos. One of the most consistent and striking phenotypes is severe disruption of the cephalo-pharyngeal skeleton. Germline and zygotic dri mutant embryos still have a recognizable dorsal bridge, dorsal and ventral arms and mouth hooks, but the H-piece and lateralgraten are missing or severely malformed. The appearance of these defects prompted an examination of genes that play a role in the formation of terminal structures. Expression of the terminal gene tailless and the genes buttonhead, empty spiracles , orthodenticle and argos was examined.