Explain why a gene can be used as a set of instructions to make a specific protein.

A gene is a segment of DNA composed of a specific sequence of bases. The order of these bases determines the sequence of codons, each codon being a triplet that specifies a particular amino acid. During transcription the DNA sequence is copied into mRNA, and during translation the ribosome reads the mRNA codons one by one, adding the corresponding amino acids to a growing polypeptide chain. The linear sequence of amino acids then folds into a specific three‑dimensional structure, giving the protein its unique shape and function. Because each gene has a distinct base sequence, it codes for a different amino‑acid sequence and therefore a different protein.