Final answer:
The transcription of the DNA triplet sequence ATC results in the mRNA codon UAG, as DNA's thymine is replaced by uracil in RNA.
Step-by-step explanation:
Transcription of the DNA triplet sequence ATC yields UAG. During the process of transcription, DNA is copied into mRNA with the nucleotides adenine (A), thymine (T), cytosine (C), and guanine (G) in DNA being replaced by adenine (A), uracil (U), cytosine (C), and guanine (G) in RNA. In this specific case, adenine (A) pairs with uracil (U) instead of thymine, and cytosine (C) pairs with guanine (G), as thymine (T) is not present in RNA. Therefore, the DNA triplet ATC would transcribe to the mRNA codon UAG.