LIFESCI 4 Lecture 12: vid 13
Vid 13
Amber mutation
• Brenner studied mutations that control the head protein of T4 phage
• Amber mutation UAG
- WT protein has full length, mutant proteins vary & shorter
- Su-: suppressor E coli
- mutation can be suppressed by being grown on amber mutant
- when utat phage grow o WT E oli, they a’t grow
- but can grow on amber suppressor E coli -> full length
- host range mutant
• nonsense mutation: when grown on WT E coli, get short protein; when grown on
suppressor strain, get full length protein
• mutated Amber suppressor has a mutation in tRNA gene
• in WT E coli, tRNA tyrosine has AUG anticodon; in suppressor E coli, tRNA tyrosine has
mutation: AUG mutated to AUC -> base pair with UAG (stop codon) -> keep translating
• suppressor mutation: reverts phenotype of the first mutation
- first mutation is nonsense mutation in phage T4 head protein
- second mutation is mutation in anticodon of tRNA tyrosine Su-
- so ut 1 a’t grow o WT, ut a grow o Aer utatio
• also can have suppression to normal stop codons
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