Question

At which side of the transcription unit, most of the RNA polymerase II promoters are located?

• A. \(3'\) downstream
• B. \(5'\) upstream
• C. Near to the C terminus
• D. Near to the N terminus

Hint:

Remember: \[ \text{Promoter} \rightarrow \text{Binding site for RNA polymerase} \]
• Upstream \(\rightarrow\) Toward \(5'\) end
• Downstream \(\rightarrow\) Toward \(3'\) end \[ \text{TATA box is usually present upstream of the transcription start site} \]

Answer 1

The Correct Option is B

Concept: A promoter is a specific DNA sequence where RNA polymerase binds to initiate transcription. For most eukaryotic genes transcribed by RNA polymerase II:
• The promoter is located upstream of the transcription start site.
• It lies toward the \(5'\) side of the coding strand. Common promoter elements include:
• TATA box
• CAAT box
• GC box These regulatory regions help RNA polymerase II and transcription factors initiate transcription.

Step 1: Understanding the position of promoters. In a transcription unit: \[ \text{Upstream} \Rightarrow \text{Toward the } 5' \text{ end} \] Most RNA polymerase II promoters are found: \[ \boxed{\text{At the } 5' \text{ upstream region}} \] This position allows RNA polymerase II to bind before transcription begins.

Step 2: Understanding downstream and terminal regions.
• Downstream refers to the direction toward the \(3'\) end after transcription begins.
• C-terminus and N-terminus refer to proteins, not DNA promoter locations. Hence, promoter regions are not described relative to protein termini.

Step 3: Eliminating the incorrect options.
• Option (A): Promoters are generally not located downstream for RNA polymerase II genes.
• Option (C): C-terminus refers to proteins, not transcription units.
• Option (D): N-terminus also refers to proteins, not promoter positions. Therefore, the correct answer is \(5'\) upstream. \[ \boxed{\text{RNA polymerase II promoters} \Rightarrow 5' \text{ upstream}} \]