Genetic Localization of the Clock Mutant Itj Neurospora’ and a Gene Modifying Its Band-size

UTANTS of Neurospora crassa have been described in which rhythms OCcur; these include patch (BRANDT 1953; PITTENDRIGH, BRUCE, ROSENSWEIG and RUBIN 1959; STADLER 1959) and timex (SARGENT 1965), in which conidia are formed with a period of about one day. Also, a growth rhythm has been described in clock (SUSSMAN, LOWRY and DURKEE 1964), in which the surface mycelium becomes increasingly dense until growth abruptly ceases except in a few hyphae (“initials”) from which the next band is formed. The original isolate of clock formed bands which were 80 mm or longer on complete medium. However, variants soon appeared in which the size was markedly altered ( SUSSMAN et al. 1964). Environmental factors such as the composition of the medium (BERLINER and NEURATH 1965; DURKEE unpublished) and temperature (SUSSMAN, DURKEE and LOWRY 1965; BERLINER and NEURATH 1965) were found to alter band size. However, even under identical environmental conditions certain strains differed so markedly in size that genetic control was indicated. The present study was initiated in order to analyze the effect on band size of a modifier gene, named mad, and to map the gene.