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 first step in gene expression would be the transcription of RNA. What happens here is that a part of the DNA is being replicated into the RNA through an enzyme. Therefore, what happens first during transcription is that, the RNA polymerase reaches the start of a gene. The answer would be B.