A point mutation is a change in the nucleotide sequence of a gene. This can result from an error during replication that is not corrected by the usual repair mechanisms. Under normal circumstances adenines and thymines should bind to one another as should cytosines and guanines. In a base substitution mutation, a non-complementary nucleotide is incorporated into the new strand. The resulting altered triplet may code for a different amino acid or even a stop codon. Here we see 4 codons and their corresponding amino acids. A change within the second triplet results in a change in the amino acid. None of the other amino acids are affected. Insertions and deletions result in frame shift mutations. The insertion of an extra nucleotide not only affects the triplet it is part of, but all subsequent triplets, thus drastically altering the protein product. The result is similar if a nucleotide is deleted.