What is a codon?

A codon is defined as a three-nucleotide sequence in messenger RNA (mRNA) that corresponds to a specific amino acid in the protein synthesis process. During translation, the sequence of codons in mRNA is read by ribosomes, and each codon specifies which amino acid will be added next during the formation of a polypeptide chain. This is a fundamental concept in molecular biology because the order of nucleotides in the mRNA determines the sequence of amino acids that make up proteins, which are essential for cellular function.

The significance of the three-nucleotide structure lies in the need for specificity in the genetic code; a three-nucleotide sequence allows for 64 possible combinations (4 nucleotides raised to the power of 3), which is sufficient to code for the 20 standard amino acids used in protein synthesis, plus start and stop signals. This gives the genetic code its robustness and versatility in forming various proteins with different sequences and functions.