The P{UAS-Brainbow1.1-M} transgene allows stochastic expression of one of multiple possible fluorescent proteins from a single transgene using P1cre mediated excision. It contains the 'Brainbow-1.1-M' cassette (PMID:17972876) expressed under the control of UASt regulatory sequences. The 'Brainbow-1.1-M' cassette contains open reading frames (ORFs) for 4 fluorescent proteins: Kusabira-Orange, mCherry, EYFP and mCer. The last three proteins are tagged with Tag:MyrPalm(mLyn) to target them to the cell membrane. Three mutually exclusive lox cassettes (loxN, lox2272 and loxP variants) are present. In the absence of P1cre recombinase the ORF adjacent to the UASt sequence, Kusabira-Orange, is expressed. In the presence of P1cre, any of the three distinct lox cassettes can be irreversibly excised. Depending on which cassette is excised, any one of the mCherry, EYFP or mCer coding regions can become juxtaposed with the UASt sequence, resulting in expression of that protein.