Mutation

돌연변이(Mutation)은 nucleotide sequence의 변화를 말한다.

분류

• Point mutations((silent, missense, and nonsense)
  • Transition: purine to purine (eg, A to G) or pyrimidine to pyrimidine (eg, C to T).
  • Transversion: purine to pyrimidine (eg, A to T) or pyrimidine to purine (eg, C to G).
• Silent mutation: Nucleotide substitution but codes for same(synonymous) amino acid; often base change

in 3rd position of codon (tRNA wobble).

• Missense mutation: Nucleotide substitution->changed amino acid (called conservative if new amino acid is similar in chemical structure)
  • Sickle cell disease(substitution of glutamic acid with valine)
• Nonsense mutation: Nucleotide substitution -> early stop codon. -> usually nonfunctional protein
• Frameshift mutation: Deletion or insertion of a number of nucleotides not divisible by 3 ->misreading of all nucleotides downstream. Protein may be shorter or longer, and its function may be disrupted or altered.
  • Duchenne muscular dystrophy, Tay-Sachs disease
• 기타
  • Splice site mutation -> retained intron in the mRNA protein with impaired or altered function.
    • Rare cause of cancers, dementia, epilepsy, some types of β-thalassemia.