As a graduate student at Princeton University, Rockefeller’s
Michael Elowitz constructed a genetic applet of his own-a clock.
In the world of digital computers, the clock is one of the most
fundamental components. Clocks don’t tell time-instead, they
send out a train of pulses that are used to synchronize all the
events taking place inside the machine. The first IBM PC had a
clock that ticked 4.77 million times each second; today’s top-
of-the-line Pentium III computers have clocks that tick 800
million times a second. Elowitz’s clock, by contrast, cycles
once every 150 minutes or so. The biological clock consists of
four genes engineered into a bacterium. Three of them work
together to turn the fourth, which encodes for a fluorescent
protein, on and off-Elowitz calls this a “genetic circuit.”
Although Elowitz’s clock is a remarkable achievement, it doesn’t
keep great time-the span between tick and tock ranges anywhere
from 120 minutes to 200 minutes. And with each clock running
separately in each of many bact