New year, new infographic.
THE Genetic Code! It’s a thing. Not a widely known thing among the general public in 2025, but it should be. There’s only one, apparently: all life forms discovered so far use the same code (rarely with a small deviation) for assembling each of their protein molecules according to the base sequence of a gene. It is a secret code no longer (completely deciphered just about exactly sixty years ago, 1966)!!
There’s no need to memorize this code - you can just look it up.
Of course, everyone should know the start codon ATG (AUG, in mRNA). This triggers the start of the amino acid chain assembly process. AUG happens to encode the amino acid methionine (M). So every protein’s amino acid sequence starts with M.
And you can remember the 3 stop codons: TGA, TAG and TAA.
A stop codon, everyone should know, is where the protein-coding sequence comes to a proper end, and the assembly process is finished. (Some great artist once said that the knack of being a good artist is knowing when to stop.)
There are 64 codons in all, of course. Four possible bases in each of three positions, first second and third. 4 x 4 x 4 = 64 possible three-base sequences, all of which must exist and which must be dealt with.
So 64 codons, minus 3 stop codons equals 61, coding for exactly 20 amino acids. As you can see, some amino acids correspond to more than one codon. Some of the more popular amino acids are matched up with three or four codons; leucine and arginine each have six! Only methionine and tryptophan have just one codon apiece.
I’ve made you a new Genetic Code chart which might be the friendliest ever for novice users. PDFs for free download are here (with mRNA codons) and here (with DNA codons). You’re welcome!
Friendliest how?
It’s a modified version of the chart on page 121 of The Way Life Works. Hoagland and Dodson’s super cute molecular rendering scheme is used, showing atoms of the side-chains as circles with kissing edges; the invariant amino acid backbone is abstracted as a cartoon chain link, minimizing visual clutter to avoid information overload.
Here’s a list of the modifications. I fixed errors in side-chain structure of several amino acids. I re-sized the different kinds of atoms to reflect their actual relative atomic radii. I replaced the book’s unconventional element color-coding with the conventional system (oxygen red, nitrogen blue, etc). I replaced the original’s arbitrary crazy-quilt background colors with a color-coding scheme for the four essential chemical personalities of amino acid side-chains: hydrophobic, polar, acidic, and basic. To further reduce visual clutter, I labeled amino acids with their one-letter abbreviations rather than their full names. (You can easily print out the list of full names and abbreviations for learners’ reference.)
Last but not least, a little box at top left introduces the start codon ATG (or AUG), and points it to methionine (M), providing the key for reading the chart.
Once learners have mastered this introductory map of the Code, they should be shown the best (imho) visualization, free on Wikipedia here: https://en.wikipedia.org/wiki/Genetic_code#/media/File:GeneticCode21-version-2.svg