Where would you find a codon?

A codon is a sequence of three nucleotides in messenger RNA (mRNA) that specifies a particular amino acid during the process of translation, which is part of protein synthesis. Each codon corresponds to a specific amino acid or a stop signal, directing the assembly of amino acids into a polypeptide chain.

In eukaryotic cells, the genetic information transcribed from DNA into RNA first exists as a pre-messenger RNA (pre-mRNA), which is then processed into mature mRNA. The mature mRNA is comprised of coding sequences that are expressed as proteins and includes the codons that determine the sequence of amino acids in the resulting protein.

Other options, like the tRNA strand, carry amino acids and have anticodons complementary to mRNA codons, but they do not contain the codons themselves. The DNA template strand serves as the blueprint for transcription and contains the corresponding DNA triplets; however, these are not codons in the context of mRNA. Introns are non-coding regions found within a gene and are spliced out during processing of pre-mRNA; they also do not contain codons. Therefore, codons are specifically found in the mature mRNA strand.