A DNA triplet has the sequence 3′-ATC-5′. After a single base mutation, the DNA triplet produces an mRNA codon that specifies the amino acid tryptophan (Trp). What mutation did the DNA triplet undergo?

Point mutation (transition)

Explanation:

mRNA has uracil instead of thymine:

3′-ATC-5′ is transcribed as UAG.

Now, since Tryptothan, an amino acid is coded by the triplet codon UGG. The single base mutation made the second nitrogenous base Adenine to become Guanine - this kind is called point mutation where a purine base substitute another purine base is called transition (a type of point mutation)