Transcription

What is the general meaning of transcription?

            Transcription meant for translating or transliterating or transfer of voice documents to written documents, etc.

What is meant by transcription in biology?

            In biology, transcription is the process where RNA being synthesized from DNA.

Detailed process of transcription:

• The double helical and highly coiled structure of DNA unwounded to start the process of transcription.  This unwinding is carried out by the enzyme called helicase.
• After the segregation of two DNA strands for a little length, the core promoter binding protein (TATA binding protein) initiates the process of synthesis of RNAs.
• RNA polymerase initiates the process of synthesis of RNA at the core promoter site.  Core promoter site is the site where the RNA polymerase recognizes and start to build nucleotides one over another for the synthesis of RNA.

Example: The good example for core promoter site is TATA box.

• The attachment of core promoter binding factor made with RNA polymerase will initiates the synthesis of RNA.
• Next, the promoter should be cleared to continue the process.  After the RNA polymerase made bond with first nucleotide, promoter of the process should be cleared.
• Then, RNA polymerase continues the bonding process between nucleotides to make the complete single stranded RNA.
• RNA polymerase reads the template strand of DNA which is in 3’ – 5’ direction, so the RNA produced in the direction of 5’ – 3’. 
• At last, the process should be terminated.  This is done by Rho – dependent and independent termination in prokaryotes.  In eukaryotes, it was not understood up to this level, but addition of Adenines (polyadenylation) followed by the transcript is found.

Difference between DNA replication and RNA transcription:

            In DNA replication, two double stranded DNAs produced from one double stranded DNA.  But, in RNA transcription, one single stranded RNA is produced from one double stranded DNA. 

            One more striking difference is nucleotides as a constituent.  Addition of uracil in RNA instead of thymine.