The sequence of amino acids in a protein is determined by the genetic code found in an organism’s DNA. Each protein is encoded by a specific gene, which is a segment of DNA that provides the instructions for assembling the amino acids in the correct order.
During the process of transcription, the DNA is copied into messenger RNA (mRNA), which serves as a template for protein synthesis. The mRNA is then translated into a protein at the ribosomes, where the sequence of nucleotides in the mRNA dictates the sequence of amino acids that are linked together to form the protein.
In essence, the sequence of nucleotides (adenine, thymine, cytosine, and guanine) in the gene correlates with specific amino acids, based on the rules of the genetic code. Each three-nucleotide sequence, called a codon, corresponds to a particular amino acid, thus determining how the protein is formed.