A particular triplet of bases in the template strand of DNA is 5′-AGT-3′. What would be the corresponding codon for the mRNA that is transcribed?

• A. 3′-UCA-5′.
• B. 3′-UGA-5′.
• C. 5′-TCA-3′.
• D. 3′-ACU-5′.

Answer: (A)

Verified step by step guidance

1. Identify the direction of the DNA template strand, which is given as 5′-AGT-3′. Remember that transcription occurs in the 3′ to 5′ direction on the template strand, producing an mRNA strand in the 5′ to 3′ direction.
2. Determine the complementary RNA bases for each DNA base. In RNA, adenine (A) pairs with uracil (U), thymine (T) pairs with adenine (A), cytosine (C) pairs with guanine (G), and guanine (G) pairs with cytosine (C).
3. Apply the base pairing rules to the DNA template strand 5′-AGT-3′ to find the corresponding mRNA sequence. The complementary RNA bases will be U for A, C for G, and A for T.
4. Write the mRNA sequence in the 5′ to 3′ direction, which is the direction in which mRNA is synthesized. The complementary sequence to 5′-AGT-3′ is 3′-UCA-5′.
5. Verify the direction and sequence of the mRNA to ensure it matches one of the given options. The correct mRNA codon transcribed from the DNA template strand 5′-AGT-3′ is 3′-UCA-5′.