Biology STAAR Practice Test – Texas Exam Prep & Study Guide

A codon is defined as a sequence of three nucleotides in messenger RNA (mRNA) that corresponds to a specific amino acid or a stop signal during the process of translation in protein synthesis. Each set of three nucleotides (for example, AUG, UUU, GGC) encodes for one particular amino acid or serves as a signal to terminate the process of translation. This triplet nature of codons is crucial because it allows for the diversity of proteins by specifying different amino acids that are linked together to form polypeptides, which then fold into proteins. Thus, identifying a codon as a sequence of three nucleotides is essential for understanding genetic coding and protein synthesis.