Final answer:
The original DNA base sequence for the given mRNA message AAC UAC UGC is TTG ATG ACG. This can be determined by the base pairing rules of transcription, where uracil (U) in mRNA pairs with adenine (A) and the other nucleotide bases pair as in DNA (C with G, and A with T in the DNA strand).
Step-by-step explanation:
To determine the original DNA base sequence from an mRNA sequence, we must first understand that during transcription, the sequence of bases in DNA is used to make a complementary sequence in mRNA. However, in RNA, uracil (U) is used instead of thymine (T). The mRNA codons are read in sets of three bases, and each codon specifies a single amino acid or a start/stop signal during translation.
The mRNA sequence given is AAC UAC UGC. To get the corresponding DNA sequence, we need to identify the complementary bases. The complementary base to A (adenine) in DNA is T (thymine), to U (uracil) in mRNA is A (adenine), to C (cytosine) in both DNA and RNA is G (guanine), and to G (guanine) in both DNA and RNA is C (cytosine).
Therefore, the original DNA sequence matching the given mRNA sequence of AAC UAC UGC would be:
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- AAC becomes TTG (A pairs with T, and C pairs with G)
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- UAC becomes ATG (U pairs with A, A pairs with T, and C pairs with G)
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- UGC becomes ACG (U pairs with A, G pairs with C, and C pairs with G)
The correct answer is TTG ATG ACG, which corresponds to option C in the question provided.