How can the DNA base sequence be deduced from a given mRNA strand?

Sourav PanNovember 8, 2024

Answered

To deduce the DNA base sequence from a given mRNA strand, one can follow a systematic approach based on the principles of complementary base pairing. Here’s how this process works:

Steps to Deduce DNA Sequence from mRNA

1. Understand the Base Pairing Rules:
   • In RNA, adenine (A) pairs with uracil (U), while cytosine (C) pairs with guanine (G). Therefore, when deducing the DNA sequence from mRNA, the following conversions apply:
     • A (in mRNA) → T (in DNA)
     • U (in mRNA) → A (in DNA)
     • C (in mRNA) → G (in DNA)
     • G (in mRNA) → C (in DNA)
2. Identify the mRNA Sequence:
   • Start with the known mRNA sequence. For example, consider the mRNA sequence: 5′-AUG UUC GAA-3′.
3. Convert mRNA to DNA:
   • Apply the base pairing rules to convert each nucleotide in the mRNA sequence back to its corresponding DNA nucleotide. The conversion should be done in the reverse direction because DNA is antiparallel to RNA.
   • For the example provided:
     • AUG → TAC
     • UUC → AAG
     • GAA → CTT
4. Write the Complementary DNA Strand:
   • The resulting DNA sequence will be complementary to the mRNA strand. For our example, if we convert each codon:
     • 5′-AUG UUC GAA-3′ (mRNA)
     • 3′-TAC AAG CTT-5′ (complementary DNA strand)
5. Determine the Coding Strand Orientation:
   • If needed, determine whether you want to express the sequence in terms of the coding strand or template strand of DNA. The coding strand will have the same sequence as the mRNA (with T instead of U), while the template strand is complementary to both.
6. Final Result:
   • The final deduced DNA sequence for our example would be written as:
     • Coding strand: 5′-TAC AAG CTT-3′
   • Alternatively, if you need it in a standard format, you can present it as:
     • 5′-TAC AAG CTT-3′ for clarity.