Question

what is the function of rna polymerase in the process of transcription? it sets the start and stop codons for transcription. it \proofreads\ dna prior to the start of transcription. it adds base pairs to the new mrna transcript.

Explanation:

To determine the function of RNA polymerase in transcription, we analyze each option:

1. Option 1: Start and stop codons are part of the mRNA sequence and are recognized during translation (or for transcription initiation/termination signals, but RNA polymerase does not "set" them as codons; codons are for translation). So this is incorrect.
2. Option 2: Proofreading DNA is done by DNA polymerase (for replication) or other DNA repair enzymes, not RNA polymerase before transcription. So this is incorrect.
3. Option 3: During transcription, RNA polymerase reads the DNA template and adds complementary RNA nucleotides (base pairs) to synthesize the mRNA transcript. This matches the role of RNA polymerase.

Answer:

It adds base pairs to the new mRNA transcript.