Transgene designed to study DNA double-strand break repair by single strand annealing (SSA). Consists of MtnB promoter/enhancer sequence followed by a 208bp fragment of MtnB cDNA sequence, a RS(I-SceI) site, a 259bp genomic MtnB fragment (corresponding to the same region of the transcription unit as the cDNA fragment), followed by EGFP. In this configuration, the EGFP protein is not expressed. EGFP protein is only expressed if a double-strand DNA break is induced at the RS(I-SceI) site by the I-SceI endonuclease, and the break is repaired by single strand annealing (SSA) of the MtnB cDNA and genomic fragments flanking the RS(I-SceI) site.