DNA, just peppered with carbon atoms
Does the thought of mutations in your DNA (and other bits of your body’s cells) scare you? Do you worry about toxins, or GMOs, or species-hopping viruses? Cancer, or growing a second head? Here’s something that may terrify you. Or, since it happens every day and you’re not dead yet, maybe comfort you.
Here’s how you mutate. Your body contains a lot of carbon. This is such a basic fact that to say a chemical is organic means it contains carbon atoms in its molecules. Your DNA, the genetic blueprint that pilots your cells through life, contains carbon atoms.
Carbon, like many elements, exists in different forms called isotopes. Mostly we have carbon-12, but a fraction of all carbon is carbon-14, which is radioactive. When it decays (that is, releases a sub-atomic particle or energy from its nucleus), it transmogrifies into a different element, nitrogen.
Isaac Asimov once estimated that this transmogrification happens roughly six times a second somewhere in the DNA in your body, every second of every day, throughout your life. I’m way too lazy to check his figures, but whatever the rate, it happens. Every one of these events mutates the DNA where it occurred. A lot of the mutations will be in body cells, and some will be in sperm or eggs (reproductive cells.) A mutation might kill the cell, cause cancer, get passed on to offspring, or do nothing discernable.
So, you are a mutant. So am I. And we’re still alive. Do you feel better? Or worse?
BTW: Carbon-14 is created in Earth’s atmosphere every day by a natural process. Cosmic radiation strikes our planet from every direction, and it includes sub-atomic particles known as neutrons. Occasionally a neutron strikes a nitrogen atom. Our atmosphere is roughly 75% nitrogen, so this is no surprise.
The neutron reshuffles nitrogen’s nucleus and transforms it to carbon-14, which is radioactive and so decays back to nitrogen. It takes 5,700 years for half of a given amount of C-14 to decay, but it happens at a steady rate. The entire process happens at a steady rate and the C-14 way up high mixes into the air down low that we breathe, so the amount of C-14 in the body of any living organism stays constant until it stops breathing (or otherwise respiring). Then radioactive decay depletes the body of C-14. This is the basis of carbon-14 dating, which you may have heard of.
BTW2: Asimov’s book is old – published in 1988 – but still worth reading. He covers a lot of history and basic science. New discoveries seldom change what we know about the basics, like radioactive decay.