WASHINGTON — Like kids taking apart a fine Swiss watch, scientists are laboring to understand what makes the biological clock that is inside every living creature tick.
Researchers have long known that bacteria, flies, worms, flowers, oak trees and human beings all have internal timepieces that keep them on a roughly 24-hour cycle.
“Living cells can actually tell the time and use this information to control their behavior,” said Hugh Nimmo, a plant biologist at the University of Glasgow, Scotland.
Many questions remain to be answered, however, such as how the clocks work at the level of individual molecules. To find out, some scientists are building simple biological clocks in a test tube.
“If you can build it, you really understand it,” said Jonathan Arnold, a geneticist at the University of Georgia in Athens. “It’s very important that we know how the clock works at the molecular level.”
“Biological timekeeping is a core property of life on a revolving planet,” said Jay Dunlap, a biochemist at Dartmouth College in Hanover, N.H., and the author of a book on the subject. “Time organization is a vital part of the survival and normal functioning of every species.”
Like clockwork
When clocks go awry, they contribute to miseries such as insomnia, liver disease and cancer, Arnold said. In humans, a gene that the biological clock controls is involved with early- morning heart attacks.
Organic timing mechanisms are governed by one or more clock genes in a cell’s DNA. The genes produce specialized proteins, long strings of organic molecules, that control the sequence of bodily functions.
Taken together, the genes and proteins make up a complex regulatory network that fits together like the gears in a watch. As in a clock, the timing can be reset to compensate for daylight saving time, night work and jet lag.
A real old timer
The simplest biological clock is probably the most ancient. It’s found in blue-green algae, also known as cyanobacteria, the one-celled creatures that create pond scum. This clock started keeping time about 3.5 billion years ago, when the world was young.
The cyanobacteria clock consists of just three proteins. One of them, shaped like a six-sided ring, looks surprisingly like a cog, or escape wheel, in a mechanical watch, according to Susan Golden, a biologist at Texas A&M University in College Station.
“The gears mesh and turn to crank out a 24-hour timing circuit,” Golden reported in the journal Proceedings of the National Academy of Sciences.
As organisms grew increasingly complex over millions of years, so did their timing mechanisms.
“In flies, worms and mice, the clock has become more elaborate,” said Arnold of the University of Georgia. “Functions once found in one protein have been separated into multiple proteins.” For example, the frequency gene in bread mold, a common fungus, controls 295 other genes, Arnold said.
Humans and other mammals have “master clocks” buried deep inside their brains in bundles of cells called the suprachiasmatic nucleus.
The suprachiasmatic nucleus coordinates peripheral clocks in other organs, including the lungs, liver and kidneys.
