Types of mutations
- Created by: kpritchard16
- Created on: 28-05-18 11:37
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- Types of mutations
- Missense mutation
- new nucleotide alters the codon so as to produce a altered amino acid in the protein product
- Sickle cell anaemia
- base 17 of beta-chain of haemoglobin is mutated from A to T
- codon 6 changes form GAG to GTG resulting in amino acid valine instead of glutamic acid
- Sickle cell anaemia
- new nucleotide alters the codon so as to produce a altered amino acid in the protein product
- Point mutation
- where a single base becomes replaced by another
- Transition
- one purine or pyrimidine is replaced by the other
- A is replaced by G or C is replaced by T
- one purine or pyrimidine is replaced by the other
- Transversion
- a purine is replaced by a pyrimidine or visa versa
- A is replaced by C or T etc.
- a purine is replaced by a pyrimidine or visa versa
- Nonsense mutation
- new nucleotide changes a codon that specified an amino acid to one of the STOP codons(TAA, TAG or TGA)
- CF
- most common mutation is delta F508 or G542X
- CF
- the earlier in the gene that this occurs, the more truncated the protein product and the more likely that it will be unable to function
- new nucleotide changes a codon that specified an amino acid to one of the STOP codons(TAA, TAG or TGA)
- Silent mutation
- most amino acids are encoded by several different codons so if one is changed, the same amino acid is still produced
- Splice site mutations
- one or more introns remain in the mature mRNA and can disrupt the protein product
- PKU
- single base change, G to A, at the 5' splice donor site of intron 12 in the phenylalanine hydroxylase gene
- splice machinery (enzymes) does not see the intron 12 donor site and uses intron 11 donor site instead
- PKU
- one or more introns remain in the mature mRNA and can disrupt the protein product
- Frameshift
- Indels cause frameshift. Often create new stop codons, resulting in a nonsense mutation
- Indels of 3 nucleotides or mutiples of three may be less serious due to reading frame being preserved
- Trinucleotide repeat diseases e.g. Huntington's disease or Fragile X syndrome
- Indels
- Insertion
- between one and several thousand base pairs may be added to DNA sequence of gene
- Deletion
- between one and several thousand base pairs may be removed from DNA sequence of gene
- Insertion
- Missense mutation
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