WITH all the fuss about the genome, one basic fact continues to surprise.
Every genetic part of us, all the codes for the colour of our skin and eyes, our
propensity for having a double chin or a flat tummy, our risk of getting certain
diseases, comes from the combinations of just four bits. Four bases, nicknamed
A, T, C and G.
Just four. Doesn’t that seem odd to you?
For me, it all sounds suspiciously like the Middle Ages when people believed
passionately that all matter was made from another four bits: earth, air, water
and fire. Well, that turned out to be a little short of the truth, didn’t
it?
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Fast-forward a few centuries and the “bit” of choice was the atom, fervently
believed to be the unbreakable building block of matter. On again and it was
protons, electrons and neutrons. Getting better, but still not quite right. Then
we found tinier bits like quarks, muons, leptons and. . . it just goes on. To
this day, all those indivisible bits keep on being divided.
Which leads me to believe that our four, holy, magical bases are very
probably not the end of the story. Imagine a day some hundred years hence. We
think we finally have the genome pegged. All the bits and genes have been
sequenced, identified and pinned down.
But, for some reason, there are still things we can’t explain. We still can’t
quite figure out why someone with a recognised mutation at, say, spot 134 on
chromosome 12 has a high chance of getting hangnails, while someone with the
same mutation, living in the same house and even using the same washing up
liquid, sails through life with perfect cuticles. Or why one identical twin is
addicted to chocolate while the other spits it out. Or why I keep killing all my
houseplants despite there being so many green thumbs in my family tree.
Then, one day, the penny drops and the jaws of all geneticists around the
world collectively fall to the floor. Some subtle change, maybe somewhere deep
down in the quarks inside the atoms of the bases, means that each of those four
bits comes in three different varieties. Tweak the quarks and what looks like an
A could be slightly, but critically, different.
Perhaps the physibiochemist who discovers this has a sense of humour. Since
we’ve used up “colours” for quarks, “flavours” for neutrinos and “spin” for
electrons, she calls this new quality “pitch”. And, for good measure, she names
the 12 new bases after musical notes. A, A flat, A sharp, C, C flat, C sharp,
and so on. She runs into a bit of trouble with T, so she renames it E
(ethymine), which makes for a surprisingly even spread across the octave.
Geneticists run for their lab equipment, with the old human genome sequence
now looking hopelessly antiquated, and start all over again. The great-grandson
of Craig Venter, who is, by chance, a pianist, promises to hold a concert and
play the genetic score when it’s completed.
It may be a tad fanciful and, to be honest, I’m not sure the physics holds
up. But it could happen. We’ve been wrong so many times before, why stop
now?