Context: The simplest known circadian clock is that of the prokaryotic cyanobacteria. Recent research has demonstrated that the circadian clock of Synechococcus elongatus can be reconstituted in vitro with just the three proteins (KaiA, KaiB, KaiC) of their central oscillator. This clock has been shown to sustain a 22-hour rhythm over several days upon the addition of ATP. Previous explanations of the prokaryotic circadian timekeeper were dependent upon a DNA transcription/translation feedback mechanism.[citation needed]

Question: What has the simplest known circadian clock?
Answer: prokaryotic cyanobacteria

Question: With how many proteins can the circadian clock of Synechococcus elongatus are needed to reproduce its effect?
Answer: three proteins

Question: What type of feedback mechanism was previously thought to be needed to sustain the clock?
Answer: DNA

Question: How long a rhythm were researchers able to sustain in the in vitro experiment?
Answer: 22-hour

Question: What were the only proteins necessary to the circadian timekeeper experiment?
Answer: KaiA, KaiB, KaiC

Question: What organism has the most complex circadian clock?
Answer: Unanswerable

Question: Where can the circadian clock of theprokaryotic cyanobacteria be reconstituted?
Answer: Unanswerable

Question: What was the minimum amount of time the clock could be sustained in vitro?
Answer: Unanswerable

Question: What three proteins needed to be removed to sustain the in vitro clock?
Answer: Unanswerable