Amino acid sequence is structurally defined as the protein molecules having a long polymer of Amino acids linked by certain bonds.
A mutation is the chemical change in DNA molecules that could lead to the proteins with different Amino Acid Sequence.
The sequence of Amino acids in proteins is determined by the sequence of nucleotides based on mRNA, that in alters is signified by the sequence of bases in DNA molecules.
Each codon (set of three) designated one amino acid.