Write short note on Transcription unit.
 

Which $RNA$ carries information from $DNA$ in protein synthesis

Define a cistron. Giving examples differentiate between monocistronic and polyeistronic transcription unit.

What function is performed by sigma factor and rho factor in the process of transcription

A transcription unit in $DNA$ is defined primarily by the three regions in $DNA$ and these are with respect to upstream and down stream end;