Effects of a Clock Mutation on the Subjective Day — Implications for a Membrane Model of the Drosophila Circadian Clock

Abstract

The fly brain, like the human brain, possesses an oscillatory system which enables the brain to form a model of the 24 hour cycle in the external environment. This oscillator is termed circadian, since it continues to oscillate in the absence of environmental cues with a period of about a day.¹ The molecular mechanism of the circadian oscillator in any organism is as yet unknown. Since the fruit fly is an excellent organism for the study of the effects of mutations on nervous system function, chemically induced mutations affecting circadian rhythmicity were isolated.^2,3 These mutations behave as alleles of a single genetic locus, per,which has been mapped by means of deletions to the 3B1-2 region of the X chromosome.^2–4 They affect the periodicity of the eclosion rhythm and the adult locomotor activity rhythm in a similar manner: the short-period allele, per ^s,shortens the period from 24 hours in wild-type to 19 hours in the mutant; the long-period allele, per ¹, lengthens the period to 29 hours; and an arrhythmic allele, per ^o, produces aperiodic eclosion and activity.