Three mutations have been introduced into the nos 3' UTR sequences; the SRE[-] mutation eliminates smg protein binding to stem-loop II, the GC/GC mutation eliminates glo protein binding to stem-loop III and the +2'(C) mutation abolishes a second smg protein binding site (SRE) in the 3' UTR.

nos^{gnosSREs-.GRH-} rescues the abdominal segmentation defects of embryos produced by nos^BN females but defects in anterior development (severely reduced head skeleton and defective head morphogenesis) are seen in these embryos. Germ cell migration is unaffected in these embryos and both germ cell and gonad morphology are normal.