Which base-pairing rule correctly converts a DNA template strand to its mRNA transcript?

Which base-pairing rule correctly converts a DNA template strand to its mRNA transcript?

• A. A → U, T → A, C → G, G → C
• B. A → A, T → T, C → C, G → G
• C. A → T, T → A, C → G, G → C
• D. A → U, T → G, C → A, G → C

Answer: (A)

Transcription uses complementary base pairing between the DNA template strand and the mRNA, with uracil replacing thymine in RNA. The template is read 3' to 5' to synthesize RNA 5' to 3', so each DNA base dictates the RNA base: A pairs with U, T with A, C with G, and G with C. This makes the mapping A → U, T → A, C → G, G → C the correct rule. Other mappings would either keep thymine in the RNA or fail to pair bases correctly, which wouldn’t produce a proper transcript.

Transcription uses complementary base pairing between the DNA template strand and the mRNA, with uracil replacing thymine in RNA. The template is read 3' to 5' to synthesize RNA 5' to 3', so each DNA base dictates the RNA base: A pairs with U, T with A, C with G, and G with C. This makes the mapping A → U, T → A, C → G, G → C the correct rule. Other mappings would either keep thymine in the RNA or fail to pair bases correctly, which wouldn’t produce a proper transcript.