This document discusses genetic code and mutations. It defines genetic code as the dictionary that identifies the correspondence between nucleotide sequences and amino acid sequences. The standard genetic code uses 64 codons made up of 3 nucleotides each to code for 20 amino acids. Characteristics of the genetic code include being almost universal, non-overlapping, degenerate, and specific. Mutations are changes in the nucleotide sequence and can be point mutations, trinucleotide repeat expansions, splice site mutations, or frame shift mutations. Point mutations may be silent, missense, or nonsense. Frame shift mutations alter the reading frame and can result in loss or addition of amino acids.