Question

Which one is correct about transcription ?

• A. 5'-OH group joins with 3'-triphosphate group
• B. RNA polymerase II enzyme needs no primer
• C. RNA chain grows in 3' → 5' direction
• D. Only the coding strand (sense strand) of DNA is transcribed

Hint:

RNA polymerase differs from DNA polymerase in one key requirement for starting synthesis.

Answer 1

The Correct Option is B

Step 1: During transcription, RNA polymerase extends the growing RNA chain by attaching the 3'-OH group of the last nucleotide to the 5'-triphosphate of the incoming nucleotide, so option (A), which reverses this pairing, is wrong.

Step 2: The new RNA strand is synthesized in the 5' to 3' direction, not 3' to 5', so option (C) is also wrong.

Step 3: It is the template strand (antisense strand) of DNA that is actually read and copied by RNA polymerase, while the coding (sense) strand has the same sequence as the RNA transcript but is not itself transcribed, so option (D) is wrong.

Step 4: Unlike DNA polymerase, RNA polymerase can begin synthesis without needing a pre-existing primer, correctly making option (B) the true statement.