RNA synthesis during transcription proceeds in which direction?

RNA synthesis during transcription proceeds in which direction?

• A. 5' to 3' direction
• B. 3' to 5' direction
• C. 5' to 1' direction
• D. 3' to 0' direction

Answer: (A)

RNA synthesis during transcription grows in the 5' to 3' direction because RNA polymerase adds each new nucleotide to the 3' end of the growing RNA strand. The enzyme reads the DNA template strand in the 3' to 5' direction, so the new RNA is built in the opposite orientation and is complementary to the template (with uracil replacing thymine). The chemical step that links nucleotides forms a phosphodiester bond at the 3' hydroxyl of the last nucleotide, driving growth toward the 3' end of the RNA chain. Directions like 3' to 5' growth or other nonsensical directions aren’t how transcription operates, since synthesis must extend from the 3' end.

RNA synthesis during transcription grows in the 5' to 3' direction because RNA polymerase adds each new nucleotide to the 3' end of the growing RNA strand. The enzyme reads the DNA template strand in the 3' to 5' direction, so the new RNA is built in the opposite orientation and is complementary to the template (with uracil replacing thymine). The chemical step that links nucleotides forms a phosphodiester bond at the 3' hydroxyl of the last nucleotide, driving growth toward the 3' end of the RNA chain. Directions like 3' to 5' growth or other nonsensical directions aren’t how transcription operates, since synthesis must extend from the 3' end.