Question

What is a promoter? Is it located at the upstream or downstream end of a transcription unit?

Short answer

The segment in which the RNA polymerase binds to the DNA to start the transcription process is the promoter. Promoters are present in the upstream end of the transcription unit.

Step-by-step solution

Definition of transcription

Transcription is the process that produces the mRNA from the DNA. The mRNA is formed from the template strand of the DNA. The template strand is known as the non-coding strand.

Explanation of promoter

Promoters initiate the process of transcription. It is the segment that binds the RNA polymerase to initiate this process. The mRNA molecules are produced from the DNA strand by the activity of the enzyme RNA polymerase.

Location of promoter

The transcription unit consists of the necessary segments for the transcription, such as promoter, structural gene, and terminator.

The direction of the 5' end is upstream of the transcription, and the 3' end is downstream of the transcription.The promoter can be found upstream of the transcription unit.

The promoter is located upstream to indicate the direction in which the transcription has to begin. An example of a promoter sequence is the TATA box, which is considered conserved sequences found in the DNA.

Hence, the promoter is the segment for binding RNA polymerase. It is located upstream of the transcription unit.