The primary structure of a protein is determined by the specific linear sequence of amino acids in its polypeptide chain. This sequence is encoded directly by the genetic information in DNA through the process of transcription and translation, where codons in the DNA correspond to particular amino acids incorporated into the protein

. Each amino acid is linked to the next by peptide bonds, forming a chain from the amino (N) terminus to the carboxyl (C) terminus. The order of amino acids is unique for each protein and dictates the protein’s ultimate three- dimensional shape and function

. In summary:

• The primary structure is the exact sequence of amino acids in a protein.
• This sequence is determined by the nucleotide sequence of the gene encoding the protein.
• Peptide bonds connect the amino acids in a linear chain.
• The primary structure serves as the foundation for all higher levels of protein structure (secondary, tertiary, quaternary).
• Any change or mutation in the DNA sequence can alter the amino acid sequence, potentially affecting protein structure and function

Thus, the primary structure of a protein is fundamentally determined by the genetic code specifying the order of amino acids during protein biosynthesis.