Question

Deduce what the six wild-type codons may have been in the mutants that led Brenner to infer the nature of the UAG codon

Answer 1

The codon is UAG which is a stop (Amber) codon as it doesn't code for any amino acid.

To identify six codons, we need 6 amino acids which will be there in the mutant protein. Following amino acids need to be inserted to continue wild-type chain & their codons:

lysine => AAA, AAG

glutamine => CAA, CAG

glutamate => GAA, GAG

tyrosine => UAU, UAC

tryptophan => UGG

SERINE => AGU, AGC, UCU, UCC, UCA, UCG

(In each case, the the Underlined codon will require a single base change to give UAG.)