I Told You So!

Actually, I probably didn’t. I don’t remember when I first heard about “junk DNA,” but I think it was before we had this site. So when I read that 99% of the human genome is irrelevant stuff that has no function, I thought: how stupid! What are the chances that the human body was designed (or evolved, it makes no difference) with 99% of our DNA being “junk”? I thought it, but I don’t think I wrote it.

Arrogance is a constant temptation: we don’t know what 99% of our DNA does, so it must not do anything! We don’t know how solar radiation affects Earth’s climate, so it must have no effect at all! You can multiply examples endlessly. Scientists are probably less prone to this sort of error than others, but they are by no means immune. Think of our forbears applying the same principle–if we can’t explain it, or don’t understand it, it must be irrelevant, or better yet, doesn’t exist at all! But we, of course, are so much more knowledgeable, so much more advanced…our own arrogance is so much more justified.

So here is the news story: Don’t throw away “Junk DNA.”

Geneticists looking for the origin of heritable diseases “now have a new sandbox to play in,” said Shaare Zedek Medical Center’s medical genetics director, Prof. Ephrat Levy-Lahad, following the discovery that so-called “junk DNA” in the human genome has an important purpose after all.

Instead of 99 percent of the genome being “irrelevant filler” – as had been thought – and only the remaining 1% of the genome of 3 billion base pairs encoding for vital proteins, the “junk DNA” serves as millions of DNA switches that power the human genome’s operating system. It thus comprises a massive control panel; without these switches, genes would not work and mutations in these regions might lead to human disease.

The locations of some four million switches were discovered and published Thursday in three journals: Nature, Genome Biology and Genome Research by an international research team of hundreds of scientists led by the University of Washington in Seattle.

It turns out that the “junk DNA” concept has been discredited for a while:

Levy-Lahad told The Jerusalem Post that “scientists haven’t called the 99% ‘junk DNA’ for years, because it became clear that it wasn’t wasted. These parts of the DNA that don’t encode for protein must have had a reason to be there, but geneticists didn’t know the purpose.”

The effort required to divine the purpose of the mysterious 99% was extraordinary:

ENCODE combined the efforts of 442 scientists in 32 labs in the UK, US, Spain, Singapore and Japan. They generated and analyzed over 15 trillion bytes of raw data – all of which is now publicly available. The study used around 300 years’ worth of computer time studying 147 tissue types to determine what turns specific genes on and off, and how that ‘switch’ differs between cell types.

That’s a great achievement. The fact that it has required so much human effort to understand even a tiny piece of how our own bodies work–have worked for many millennia–should be, some would say, a cause for humility.

Images courtesy of Shutterstock.


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