When does
transcription
happen?

Transcription begins when RNA polymerase binds to a promoter sequence near the beginning of a gene (directly or through helper proteins). RNA polymerase uses one of the DNA strands (the template strand) as a template to make a new, complementary RNA molecule. Transcription ends in a process called termination.

Explanation:

Transcription Initiation. The first step in transcription is initiation, when the RNA pol binds to the DNA upstream (5′) of the gene at a specialized sequence called a promoter (Figure 2a). In bacteria, promoters are usually composed of three sequence elements, whereas in eukaryotes, there are as many as seven elements ...

when RNA polymerase binds to a promoter sequence near the beginning of a gene