Using mutagenesis by ethyl methane sulfonate, the authors investigated potential genes controlling the circadian clock in Drosophila melanogaster. Mutagen-exposed males were mated to attached-X females resulting in offspring carrying the father’s mutated X chromosome. These offspring were then screened for alterations in the circadian rhythm of eclosion and locomotor activity.
From the resulting offspring, 3 mutants with altered rhythms were found. The first mutant identified was arrhythmic for both eclosion and locomotor activity. The second mutant displayed a short circadian period in eclosion and activity of approximately 19 hours. The third mutant produced long period rhythms in circadian eclosion and locomotor activity of about 28 hours. The locations of these mutations were mapped by assessing genetic recombination with known markers on the Drosophila X chromosome. The authors found that all 3 rhythm mutations mapped to a similar position on the left end of the X chromosome.