14. Briefly describe the following:
Transcription- It refers to the process of copying genetic information from one strand of DNA into mRNA. In transcription, only one strand is copied into the RNA. While copying, the place of adenine is taken up by uracil. The transcription of DNA includes a transcription unit. The transcription unit is consists of a promoter, the structural gene and a terminator. The strands that have polarity 3’-5' act as a template and called template strand while the other strand is called coding strand. A schematic structure of a transcription unit is given below.
The promoter is located at the 5’ end and it binds the enzyme RNA polymerase to start transcription. Sigma factor also helps in initiation of the process of transcription.The terminator is located at 3’end of coding strand and usually defines the end of transcription where rho factor will bind to terminate transcription.