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: Nucleotide substitution but codes for same(synonymous) amino acid; often base change
in 3rd position of codon (tRNA wobble).
- Missense: 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: Nucleotide substitution -> early stop codon. -> usually nonfunctional protein
- Frameshift: 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.
- Splice site: Mutation at a splice site retained intron in the mRNA protein with impaired or altered function. Rare cause of cancers, dementia, epilepsy, some types of β-thalassemia.