UAS regulatory sequences drive expression of vn in which the endogenous EGF domain has been replaced with a chimeric EGF domain. The chimeric EGF domain consists of the A and B loops of the spi EGF domain and the C loop of the aos EGF domain.
visible, with Scer\GAL4ptc-559.1
anterior crossvein, with Scer\GAL4ptc-559.1
83% of wings lack the anterior crossvein in flies expressing argos::spi::vnS4A.Scer\UAS under the control of Scer\GAL4ptc-559.1.