Missense mutations are those in which a single base change (point mutation) results in a codon that encodes for a different amino acid residue. The effects of these types of mutations can range from very minor or even undetectable to major, depending on the impoance of the altered residue to protein folding and function. Nonsense mutations are also point mutations in which the affected codon is altered to a stop (nonsense) codon, resulting hi a truncated protein. Frame shift mutations are due to one or two base "pair inseions or deletions such that the reading frame is altered. These mutations generally lead to truncated proteins as well, since in most protein coding regions the unused reading frames contain numerous stop codons.