S3.05 - Poop, pus and the Manhattan Project: How we learned to spell the genetic alphabet
Kat: Hello, and welcome to Genetics Unzipped - the Genetics Society podcast, with me, Dr Kat Arney.
If you know a bit of biology, you might know that the genetic code of DNA is written in just four ‘letters’ - A, C, T and G. You may even know that these letters are the initials of the names of the molecules that make up the double helix, known as nucleotide bases: adenine, cytosine, thymine and guanine.
But where did those strange-sounding names come from?
In this episode of Genetics Unzipped, we go from poop to pus to atomic weapons on our journey to learn about the discovery of these vital chemicals and how they got their names.
Before we start, just a reminder that you can find us on Twitter @geneticsunzip or by email, podcast@geneticsunzipped.com - we know you’re listening all over the world, so come say hi! Also please do take a moment to rate and review us on Apple podcasts, if that’s how you’re listening. Or you could just tell a friend - send out a tweet, ping it over in an email or tell them in the pub. It all helps more people discover the show.
DNA, or deoxyribonucleic acid as it’s more formally known, usually comes in the form of a double helix - a twisted ladder of life. The struts of the ladder are made from chains of identical deoxyribose sugar molecules (hence the name), each interspersed with little acidic linkers called phosphate groups. So far, so boring.
The interesting stuff is the rungs, which are made of paired chemicals called bases - adenine always pairing with thymine across the gap, cytosine always pairing with guanine. A with T, C with G. And it’s the order of these bases up the ladder that spells out the instructions encoded within genes, and all sorts of other useful directions within the genome. It’s a simple genetic alphabet capable of spelling out all the recipes of life.
Breaking down the structure of DNA a little bit further, each sugar molecule plus one phosphate group plus a base (whether that’s A, C, T or G) adds up to form what’s known as a nucleotide - the fundamental building block of DNA.
Each base consists of either one or two conjoined rings of carbon and nitrogen atoms, with a couple of oxygen atoms chucked in here and there for good measure. Cytosine and thymine are each a single ring, known as a pyrimidine, while adenine and guanine have double rings and are called purines.
And if you’d like an easy way to remember which bases are pyrimidines and which are purines, you can use my handy memory aid:
Just remember, purine rhymes with tureen - a vessel that’s often made from silver. The chemical symbol for silver is Ag, so the purine bases are adenine and guanine. Snappy, right? (Well, it worked for me…)
Today, the four letters of life are starting to make their way into the public consciousness, even if most people aren’t familiar with the full names of these nucleotides.
Even so, their initials are ingrained into the scientific lexicon and burned into the brains of anyone who’s ever worked with or even just learned about genes, genomes and DNA. It’s a code that’s as inseparable from genetics as the double helix itself.
It might therefore be surprising to learn that scientists knew that DNA was made up of these four iconic chemicals - adenine, cytosine, thymine and guanine - long before its double helical structure was figured out in the 1950s.
So when were they discovered? And how did they get their unforgettable names? To find out, we need to go back to the bird poop boom of the 1840s…
The Bird Poop Revolution
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From Poop to Pus
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Nuclear Nucleotides
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That’s all for now. Next time we’ll be tackling some of the myths and misconceptions surrounding genetics and genomics - Are mutations always bad? If you’re more like your mum, does that mean you’ve inherited more of her genes? And is there such a thing as a perfect genome?
You can find us on Twitter @geneticsunzip and please do take a moment to rate and review us on Apple podcasts - it really makes a difference and helps more people discover the show.
Genetics Unzipped is presented by Kat Arney, with additional research and scripting by Emily Nordvang, and produced by First Create the Media for The Genetics Society - one of the oldest learned societies in the world dedicated to supporting and promoting the research, teaching and application of genetics. You can find out more and apply to join at genetics.org.uk
Our theme music was composed by Dan Pollard, and the logo was designed by James Mayall, and production was by Hannah Varrall. Thanks for listening, and until next time, goodbye.
Music and SFX:
All music and sound effects licensed from Envato or Epidemic Sound.
