The FRT-cm-FRT cassette is designed to allow chloramphenicol selection in prokaryotic cells.
The prokaryotic promoter gb2 driving the gene for chloramphenicol resistance is a slightly modified version of the Em7 promoter. It mediates higher
transcription efficiency than the generally used Tn5 promoter. A synthetic polyadenylation signal terminates the chloramphenicol expression. The cassette is flanked by FRT sites for later excision by Flp Recombinase. Unique NotI and XhoI sites flank the cassette for convenient cloning with restriction sites.