To determine the base sequence of the DNA gene that codes for the mRNA codon AGU (which codes for the amino acid serine), we need to derive the DNA sequence that would transcribe into the mRNA.
mRNA is synthesized from the DNA template strand through a process called transcription, and the relationship between DNA and mRNA is such that the mRNA is complementary to the DNA template strand.
The mRNA codon AGU would have been transcribed from the following DNA sequence on the template strand:
- mRNA codon: AGU
- DNA coding strand (which is the same as the mRNA sequence except for the substitution of U with T): ACT
- DNA template strand (complementary to the coding strand): TGA
Since the coding strand of DNA corresponds to the same sequence as the mRNA (with thymine instead of uracil), we have:
- mRNA codon: AGU
- DNA coding strand: TCA
Therefore, the answer is TCA.
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