Figure 1.

 Cross-reactivity of anti-Poxm antiserum. A heterozygous Df(3R)dsx^D+R5 embryo (A), a homozygous Df(3R)dsx^D+R5 embryo (B), and a homozygous Df(4)G embryo (C) were probed with the anti-Poxm antiserum to demonstrate the cross-reactivity of the antiserum in embryos lacking the poxm locus (B) or the locus of the cross-reacting antigen (C). A wild-type embryo (D) was hybridized in situ with a digoxigenin-labeled cpx1 cDNA, which encodes the cross-reacting antigen and was isolated by immunoscreening a cDNA expression library with the anti-Poxm antiserum. Lateral views of stage 13 embryos are shown with their anterior to the left and their dorsal sides up.