2.11—Genetic code

The genetic code is a triplet code: each three-base codon specifies one amino acid or a start/stop signal. Codons are read sequentially and non-overlapping on mRNA.

There are more codons than amino acids, so the code is degenerate: several codons can specify the same amino acid. This can make some substitutions silent but does not make every mutation harmless.

Changing a base in a codon may leave the amino acid unchanged, replace it with another, or create a stop codon. The outcome depends on the codon and on where it occurs in the coding sequence.

Translate from the correct start codon in the correct reading frame, then stop at a stop codon. A one-base insertion can shift every downstream triplet.

“Universal” means broadly shared across organisms, not that every codon has multiple meanings. Triplets are read on mRNA during translation, not as overlapping DNA words.