A modified orb2 genomic fragment has been inserted into the attP site present in orb2^attP via phiC31-mediated recombination. The resulting allele contains an insertion of a single nucleotide in the A isoform specific exon, and a deletion of a nucleotide from an exon common to orb2 isoforms A and B. These mutations restore the isoform A reading frame (which is tagged at the C-terminal end with GFP) whilst disrupting that of orb2B. In addition, four point mutations have been introduced into the orb2 RBD domain, resulting in the amino acid changes Y492A, F494A, R601A and F604A. A single mFRT11 site is present downstream of the orb2 coding sequence, and single attL and attR sites (generated during the recombination process) are also present.