Figure 1.—

Structure of RS elements. (A) The orientation of RS3 and RS5 elements and their recombination products. 5′ and 3′ exons of the mini-white are marked by the open (RS3) or shaded (RS5) boxes. P-element ends are indicated by the triangles. FRT sites are designated by the solid arrows. (B) Recombination between an RS3r and an RS5r element in trans can generate a w⁺ deletion (I) or a w deletion (II), depending upon the relative orientations of the elements with respect to the chromosome. (C) Molecular strategies for confirming deletions (see materials and methods for details). The RS elements are as described in A. The locations of the primers described in materials and methods are shown as thin arrows with size of the PCR product indicated below each product.