Which of the following steps happens first during transcription?
a. rna polymerase reaches the end of the gene.
b. rna polymerase reaches the beginning of a gene.
c. rna polymerase pulls apart the double helix.
d. rna polymerase produces mrna from dna.

The correct answer is -

B. RNA polymerase reaches the beginning of a gene.

Explanation:

Transcription is a phenomenon of synthesis of mRNA (messenger RNA) using a template DNA, which takes place with the help of enzyme RNA polymerase.

This enzyme reaches the site from where the gene begins and thus follows its transcription using a DNA template.

It adds nucleotides in the direction 5' to 3' that is complementary to the DNA template.

Therefore, to begin the process, enzyme RNA polymerase reaches the start site of gene.

Thus, option B) is the right answer.