As can be seen, clinically important missense mutations generally change the properties of the coded amino acid residue between being basic, acidic, polar or nonpolar, while nonsense mutations result in a stop codon.

In the case of cancers, mutations cause aggravation of the conditions by impairing tumor suppressors or activating oncogenes.

Every U (uracil) in the mRNA corresponds to a T (thymine) in the original DNA. Therefore, mutations are often noted using T rather than U.

• Sickle-cell disease: GAG to GTG in the hemoglobin gene ^[1]
• Huntington's disease: CAG insertions, which adds a string of glutamines to Huntingtin^[1]
• Friedreich's ataxia: In most cases, the mutant frataxin gene contains expanded GAA triplet repeats in the first intron;^[2]
• Dentatorubral-pallidoluysian atrophy (DRPLA), caused by an expansion of a CAG repeat encoding a polyglutamine tract in the atrophin-1 protein.^[3]
• Kennedy's disease, caused by expansion of a CAG repeat in the first exon of the androgen receptor gene.^[4]
• Fragile X Syndrome: CGG insertions on the X chromosome.^[1] Practically, however, these are not related to arginine, because the mutations are located in the 5' untranslated region.
• CTG in myotonic dystrophy.^[5]
• Spinocerebellar ataxia. Many types are caused by CAG repeats, see Wikipedia:Spinocerebellar ataxia#Treatment and prognosis for details.
  • Spinocerebellar ataxia: CTG ^[6]
• β-thalassemia (β-globin gene)
  • C to U resulting in stop signal UAG ^[7]
  • also UGG to UGA^[8]
• D1822V by GAC->GTC^[9] is the most common missense APC variant described to date in colorectal cancer.^[10]
• A49T (GCC to ACC)^[11], V63M and V89L^[11] are the most common missense substitutions in prostatic or type II steroid 5alpha-reductase gene in prostate cancer tissue.^[12]
• p.R50X is the most common nonsense mutation in myophosphorylase in McArdle's disease,^[13] the most common Glycogen storage disease