What does the code in a codon specify?

The code in a codon specifies a specific amino acid or a termination signal because codons are sequences of three nucleotides in mRNA that correspond to the amino acids during protein synthesis. Each of the 64 possible codons is linked to one of the 20 standard amino acids or signals the termination of protein synthesis (stop codons). This function is fundamental to the process of translation, where the genetic information carried by mRNA is decoded to produce a functional protein. The specificity of codons ensures that the correct amino acids are incorporated into the growing polypeptide chain, ultimately determining the protein's structure and function. The alignment of codons with their corresponding amino acids is a crucial aspect of molecular biology, making this choice the correct answer.