Mutations are alterations in DNA
that can be inherited, or arise spontaneously via DNA replication
errors, environmental stressors, or random chance. A point mutation is caused by base substitution - when one nucleotide base is replaced with another. A silent mutation is when a point mutation results in a codon that codes for the same original amino acid, while a missense mutation is one where the alteration results in a different amino acid. Frameshift mutations occur with an addition or deletion of a nucleotide base that subsequently change the triplet reading frame of the mRNA codons and a nonsense mutation is any mutation that changes the triplet mRNA codon into a stop codon.