The Universal Language of Life
The genetic code is one of the most profound discoveries in biology: a simple lookup table that converts three-letter RNA words (codons) into the 20 amino acid building blocks of proteins. First cracked by Marshall Nirenberg and Har Gobind Khorana in the 1960s, this code is shared by virtually all life on Earth — from bacteria to blue whales — providing powerful evidence for the common origin of all living things.
From mRNA to Protein
Translation begins when a ribosome binds to an mRNA molecule and reads it in triplets (codons) from the 5' to 3' end. Each codon is recognized by a transfer RNA (tRNA) carrying the corresponding amino acid. The ribosome catalyzes peptide bond formation between successive amino acids, building a growing polypeptide chain. This simulation animates this process, showing the ribosome sliding along the mRNA and assembling the protein codon by codon.
The Degeneracy Shield
With 64 possible codons but only 20 amino acids (plus stop), the genetic code is redundant — most amino acids are encoded by multiple codons. This degeneracy is not random: synonymous codons typically differ only at the third (wobble) position. This means that roughly one-third of all possible point mutations are silent — they change the DNA sequence but not the protein. This built-in error tolerance is one reason life is robust against spontaneous mutations.
When Mutations Strike
Not all mutations are silent. A substitution that changes the amino acid (missense mutation) may alter protein folding or function — sickle cell anemia results from a single A→T change converting glutamic acid to valine. Worse still, an insertion or deletion of one or two nucleotides shifts the entire reading frame (frameshift mutation), garbling every downstream codon. Toggle the mutation controls in this simulation to see these effects firsthand.