The start and end of the DNA region to be transcribed in a protein-encoding gene are marked by a promoter and a terminator, respectively. Option 3 is the correct option.
For a protein-encoding gene, the start and end of the DNA region that will be transcribed are marked by specific sequences. The promoter is the sequence where the transcription machinery binds and initiates transcription. It usually exists upstream of the genes it regulates and it determines the frequency of transcription of the corresponding gene. The terminator is the sequence that signals the end of transcription and typically lies downstream of the transcribed gene region. Therefore, the correct answer to which markers define the start and end of the transcribed region is a promoter and a terminator. Option 3 is the correct option.
The appropriate question is:
For a protein-encoding gene, what marks the start and end of the DNA region that will be transcribed?
multiple choice
1) a promoter and a repressor
2) an operator and a repressor
3) a promoter and a terminator
4) a sigma factor and an operator