question_answer

The transcription unit is:

A)  TATA box to start point

B)  TATA box to stop codon

C)  Start point to stop codon

D)  35 sequence to start point

Correct Answer: B

Solution :

The transcription unit is that stretch or sequence of DNA that is transcribed into a single RNA molecule. A typical transcription unit has a promoter, a start site, a coding region and a terminator sequence at the end. Promoter is that sequence of a transcription unit where RNA polymerase binds and initiates transcription. E. coli promoter have the following is consensus sequences [a] Start point is the site within a promoter from which transcription begins. [b] - 10 sequence is 10 bP upstream of the start point and has consensus sequence TATAAT. This is commonly known as Pribnow box. [c] - 35 sequence is on 35 bP upstream of the strat point. It has consensus sequence TTGACA. [d] The distance between -10 to -35 sequences is 16-18 and seems to be critical for proper orientation of RNA polymerase   during    transcription initiation.