The P{GSV6} element contains UASt regulatory sequences at its 5' end, oriented so that in the presence of a GAL4 driver, transcription from UASt is directed outwards from this end of the element. This can result in misexpression of neighbouring genomic loci when the element is inserted in the genome. In addition it contains a Avic\GFPS65T.UAS.cAa marker allele at the 3' end; this acts as an internal reporter of the expression pattern of the GAL4 driver used. A w+mGS marker is also present.