Circadian clock: genetic characterization of a short period mutant of Chlamydomonas reinhardii.

The periods in wildtype (25 hours) and short period mutant (18 hours) of Chlamydomonas reinhardii show substantial fluctuations. Due to the considerable difference between both period types of more than 6 hours the frequency distributions of the period recordings obtained from both strains are sufficiently well separated. Crosses between both strains give rise to a progeny consisting of the short as well as the wildtype period. In about 30% of the zygotes one of the daughter strains does not show any rhythmicity and is called arrhythmic. The role of arhythmicity in the genetic representations of short and wildtype period is discussed in detail.