The most common and basic enhancer traps are: P[lacZ] from the bacterium E. coli and P[GAL4] from yeast. There exists a large number of fly stocks containing GAL4 insertions and an equally large number of fly stocks containing an UAS DNA sequence followed by a gene of interest, which permits the expression of a large number of genes with different GAL4 "drivers". Rather than generating transgenic flies with the enhancer linked directly to the gene of interest (which takes about a year , if you are starting without the appropriate DNA construct), you simply mate (cross) one transgenic fly  with another transgenic fly.Andrea Brand and Norbert Perrimon (1993). Targeted gene expression as a means of altering cell fates and generating dominant phenotypes. Development, 118, pp 401-415.D. J. Finnegan (1992). Transposable elements. Current Opinion in Genetics and Development, 2, pp 861-867.J. A. Fischer, E. Giniger, T. Maniatis and M. Ptashne (1988). GAL4 activates transcription in Drosophila. Nature, 332, pp 853-856.
The most common and basic enhancer traps are: P[lacZ] from the bacterium E. coli and P[GAL4] from yeast. There exists a large number of fly stocks containing GAL4 insertions and an equally large number of fly stocks containing an UAS DNA sequence followed by a gene of interest, which permits the expression of a large number of genes with different GAL4 "drivers". Rather than generating transgenic flies with the enhancer linked directly to the gene of interest (which takes about a year when starting without the appropriate DNA construct), one transgenic fly is simply mated (crossed) with another transgenic fly.Andrea Brand and Norbert Perrimon (1993). Targeted gene expression as a means of altering cell fates and generating dominant phenotypes. Development, 118, pp 401-415.D. J. Finnegan (1992). Transposable elements. Current Opinion in Genetics and Development, 2, pp 861-867.J. A. Fischer, E. Giniger, T. Maniatis and M. Ptashne (1988). GAL4 activates transcription in Drosophila. Nature, 332, pp 853-856.
R
, if you are
when
D
you simply mate (cross)
A
is simply mated (crossed)