Carries T583A and S596A amino acid substitutions.
In a homozygous per01 genetic background, perT583A.S596A.T:Ivir\HA1.T:Zzzz\His6 transgenic flies exhibit ultrashort circadian locomotory rhythms with approximately 16 hour periods.
In a wild-type genetic background, perT583A.S596A.T:Ivir\HA1.T:Zzzz\His6 transgenic flies exhibit shortened circadian locomotory rhythms with approximately 21 hour periods.