nonsense mutations
These mutations may result in a protein with the same function, with altered function, or with no function. Silent mutations , as they code for the same amino acid, will have no altered effect on the protein. Missense mutations may have a minor effect or a dramatic effect on the protein. Nonsense mutations usually have the most dramatic effet. Depending on the position of the premature stop codon, nonsense mutations may result in an unstable mRNA that cannot be translated, or in a truncated mRNA and a much "smaller" protein without any significant activity.