Answer: 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)