Table 1.

Mammalian Circadian Clock Genes; the Corresponding Genes in the Fruit Fly, Drosophila; and the Effects of Changes (i.e., Mutations) in Those Genes on the Behavior (i.e., Phenotype) of the Affected Animals

Mouse Gene	Alias	Drosophila Gene	Mutant Phenotype
*Clock		dClock	Lengthened period; loss of persistent rhythmicity in constant conditions
mPer1		period	Reduced amplitude, shortened period, or loss of rhythm
*mPer2		period	Shortened period, loss of rhythm
*mPer3		period	Modest shortening of period
*CKIɛ	tau (hamster)	doubletime	Shortened period in hamster mutants
*mCry1 mCry2		dcry	Animals lacking the mCry1 gene (i.e., mCry1 knockouts) have shortened period; mCry2 knockouts have lengthened period; animals lacking both genes (i.e., double knockouts) have a loss of rhythm
*BMAL1	MOP3	cycle	Loss of rhythm
?mTim		timeless	Role in mammals is not clear
?DBP			Modest lengthening of period

NOTE: Asterisk (*) indicates that a key role for the gene in timekeeping has been demonstrated by the phenotype of a mutant.