Researchers at the University of Pennsylvania and the Salk Institute conducted a whole, well, we need to make a collective noun for "gigantic number of genetic analyzes" to describe it. They analyzed thousands of genes over one hundred and fifty times, taking RNA samples from lab mice once an hour for two days. Or more likely, they took them during the day and their grad students took them at 4 am.
The results showed time-varying expression of thousands of genes. There were over 3,000 24-hour cycling genes in the liver alone, and these mice don't even drink. Such day-cycles have already been observed, but the surprise was hundreds of 12-hour cycles and more than sixty 8-hour shifts, creating the image of tiny rodent genes rushing to work on a little genetic subway.
Don't worry, this won't lead to a new army of gengineered überworkers (or Gattaca style-screening for people who'll automatically do overtime) - imagining that your genes simply tell you what to do is simplistic, and a pretty weak cop-out to boot. It would be a mistake to think this study shows eight hours as optimal for humans. Your genes are part of the entire system that is you, with all the inputs and stresses you're subjected to, and many gene expression patterns are reactions to your behavior, not the cause. The scientists grew mouse liver cells in petri dishes and these "Never even squeaked" cells expressed only the automatic 24-hour cycles: they'd never seen dawn, dusk, or feeding time, so the shorter cycles were absent.
Confirming this, the scientists were able to erase one of the 12-hour peaks by changing the feeding time of the mice. So these cycles aren't the key to creating extra hours for humans, but they can help with a whole host of circadian sicknesses for those who need to work according to different clocks - a potential issue for longer-range astronauts. Symptoms of circadian sicknesses can include fatigue (duh), dizziness, and Level 60 Night Elves.
Posted by Luke McKinney.
Biological Basis for 8-hour Clock. http://www.sciencedaily.com/releases/2009/04/090423132952.htm
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