A sequence cassette encoding 2A-EGFP has been inserted at the C-terminal end of the clumsy open reading frame. In addition, two FRT sites have been inserted, to produce an artificial FRT cassette that includes clumsy coding sequence and the 2A-EGFP cassette (a single loxP site is also present, downstream of the second FRT site). This results in a conditional allele; FLP recombinase can be used to excise the artificial FRT cassette, excising the 2A-EGFP sequence and removing clumsy coding sequence, disrupting its function.