A true reversion occurs when the wild-type DNA sequence is restored to encode its original message by a second mutation at the s
ame site or within the same cod on. Which of the following isoleucine codon(s) could be mutated once to form a methionine codon, and then mutated at a second site to restore an isoleucine codon? Select all that apply. (Note that two different positions in the codon must be mutated.) AUC
AUU
AUA
none of these codons
In order for mutation to occur to form methionine codon from an isoleucine codon, position 3 must be changed to a G, giving AUG. A secind mutation would then be required at a second site in the AUG codon. since the isoleucine codons, AUA, AUC and AUU does not have a G at position 3, a true reversion can't occur without mutating the position 3 again.
