Construct: 13.2kb of D.simulans per with the central 700bp thr-gly repeat region replaced by that of D.melanogaster.
A SstI-BamHI fragment (carrying the Thr-Gly repeat) of D.melanogaster per is substituted into Dsim\per+t13.2.
Circadian periodicity longer than that of wild type.
Male D.melanogaster per01 flies carrying per::Dsim\perTGm produce courtship songs with a period of about 55-58 seconds, characteristic of D.melanogaster.