Final answer:
The order of codons is determined by the DNA sequence, which is transcribed into messenger RNA (mRNA). The mRNA's sequence of nucleotides, read as codons, dictates the specific sequence of amino acids in a protein.
Step-by-step explanation:
The order of codons in a protein is ultimately determined by the sequence of bases in the DNA. During the process of transcription, the DNA sequence is copied into messenger RNA (mRNA), with the bases being complementary (except that uracil replaces thymine). This newly formed mRNA sequence is what determines the order of amino acids in a protein, as it is later read by the ribosome during the process of translation.
The genetic code is universal and redundant, meaning that the sequence of nucleotides on the mRNA is read in sets of three bases known as codons. Each codon corresponds to a specific amino acid or a start/stop signal that guides the synthesis of proteins by determining the sequence in which amino acids are added to the growing polypeptide chain.
Therefore, the correct answer to the question is "The DNA sequence determines the order." The genetic code's instructions are initially encrypted within the DNA and are then transcribed into mRNA. The RNA sequence reflects the instructions for the amino acid sequence, being a complementary copy of the DNA's coding region, but it is indeed the original DNA sequence that sets the order of the genetic code which, in turn, determines the codons for a protein.