What is the only start codon in the genetic code?

The start codon in the genetic code is AUG. This codon is significant because it signals the beginning of protein synthesis in cells. AUG encodes the amino acid methionine, which is the first amino acid incorporated into a growing polypeptide chain during translation.

In the genetic code, codons are combinations of three nucleotide bases that correspond to specific amino acids or signal the start or end of protein synthesis. While there are multiple stop codons, such as UAG and UAA, which signal termination of translation, AUG exclusively serves as the start codon. The codon CAC encodes the amino acid histidine and does not play a role in signaling the start of translation. Thus, AUG's unique role as the sole start codon highlights its importance in the process of gene expression and the synthesis of proteins.