What does the RNA coding region include?

The RNA coding region encompasses everything from the transcription start site to the termination site. This includes not only the coding sequences that will ultimately translate into proteins but also regulatory elements that can be involved in the transcription process itself. The transcription start site is where RNA polymerase binds to initiate transcription, and it is critical for determining where the RNA molecule begins to be synthesized. The termination site marks the end of transcription, signaling when RNA polymerase should stop adding nucleotides to the growing RNA strand.

While the entire coding sequence is technically part of the RNA coding region, the term "coding region" more broadly refers to the span from the initiation of transcription to its conclusion. Therefore, choosing the option that includes both the start and the end of this transcription process accurately captures the entirety of what the RNA coding region entails. This includes both exons, which are the sequences that code for proteins, and potentially some non-coding regions, depending on the specific context of the RNA being synthesized.