For example, proteins consist primarily of a linear arrangement of twenty different amino acids. Sub-groups of amino acids share chemical properties. Amino acids in the same group, which have similar chemical properties, can usually substitute for one another with no effect on protein structure or function. If a claim refers to a specific protein sequence, a conservative amino acid substitution can result in a new protein sequence that performs the same as the claimed one. If the claimed protein sequence was added as part of a narrowing amendment, the new sequence will not infringe under the doctrine of equivalents, even though the substitution is an insubstantial difference, and the new protein performs the same function the same way with the same result as the claimed protein.
Genes are also redundant.
They consist of a linear sequence made up of four different nucleotide bases in some distinctive order. Groups of three contiguous bases in the gene form a codon. Consequently, there are typically at least two codons for each amino acid. If a gene claim refers to a specific nucleotide sequence, substitution of a degenerate codon can yield a new gene that encodes the same protein. If the claimed gene sequence was added as part of a narrowing amendment, the new sequence will not infringe under the doctrine of equivalents, even though the substitution is an insubstantial difference, and the new gene performs the same function the same way with the same result as the claimed gene.