Not every gene mutation causes alteration in the composition of the protein the gene codifies. Since the genetic code is degenerated, i.e., there are amino acids codified by more than one different DNA nucleotide triplet, if by chance the mutation substitutes one or more nucleotides of a codifier triplet and the newly formed triplet still codifies the same amino acid codified by the original triplet there will be no modification in the protein made from the gene.
