Question

Differentiate between the process of transcription in prokaryotes and eukaryotes ?

Answer 1

Transcription is the process of formation of RNA from DNA.

In prokaryotes:

• The structural genes are polycistronic and continuous.
• A single DNA dependent RNA polymerase catalyses the transcription of all three types of RNA that is mRNA, tRNA & rRNA
• The DNA strands unwind and one of the strands (3' → 5’) acts as the template strand.
• The RNA polymerase binds at the promoter site for transcription.
• It uses ribonucleotides for polymerization on a DNA template following complementary of bases.
• As unwinding continues, the new strand of RNA also elongates. Polymerisation occurs in the 5’ → 3’ direction.
• When RNA polymerase falls on the terminator sequence, the synthesis stops and the new RNA strand is liberated.

In Eukaryotes:

• The structural genes are split.
• They have exons interspread with introns. (the coding and non coding sequence respectively)
• The primary transcript of RNA undergoes splicing, by which the introns are removed and the exons are joined together.
• The hnRNA undergoes two additional processes called, capping and tailing to become mRNA.
• Methyl guanosine tri phosphate is added to the 5’ end of hnRNA in capping.
• Adenylate residues (about 200 – 300) are added at the 3’ end in tailing.
• The fully processed hnRNA is called mRNA is released from the nucleus into the cytoplasm.