A base-pair substitution is the replacement of one nucleotide and its partner with another pair of nucleotides. Some substitutions are called silent mutations because, owing to the redundancy of the genetic code, they have no effect on the encoded protein. In other words, a change in a base pair may transform one codon into another that is translated into the same amino acid. For example, if 3?-CCG-5? on the template strand mutated to 3?-CCA-5?, the mRNA codon that used to be GGC would become GGU, but a glycine would still be inserted at the proper location in the protein. How could such a substitution influence the protein produced?