Final answer:
The mRNA sequence that complements the DNA sequence of ATT-GCC is UAA-CGG, where adenine pairs with uracil and cytosine pairs with guanine during transcription.
Step-by-step explanation:
The mRNA sequence that complements the DNA sequence of ATT-GCC is UAA-CGG. In DNA transcription, adenine (A) pairs with uracil (U) in RNA, and cytosine (C) pairs with guanine (G). Thus, each adenine (A) in the DNA sequence is transcribed to uracil (U), and each thymine (T) in DNA is transcribed to adenine (A) in RNA. The cytosine (C) in DNA remains cytosine (C) in the mRNA, and the guanine (G) in DNA remains guanine (G) in the mRNA.