Transcription in Prokaryotes & Eukaryotes

Transcription in Prokaryotes & Eukaryotes: An Overview

Transcription: Overview

In Transcription only a part of DNA is transcribed.

RNA Polymerase binds to the Promotor but not to the coding region.

The gene to be transcribed has a double stranded DNA structure but only one strand is transcribed that is called the Template strand.

The mRNA complimentary to this Template strand.

Coding strand of the gene is NEVER used.

The mRNA produced is identical to the Coding strand but, as we all know there is no Thymine (DNA only), so Thymine (T) is replaced by Uracil (U) in the mRNA.

Q: Is Promotor region Transcribed?

Ans: NO. RNA Polymerase starts at +1

Comparison of RNA Polymerases in Prokaryotes & Eukaryotes

Prokaryotic RNA Polymerase

Single RNA Polymerase (α2ββ’)
Requires sigma(σ) to initiate at a promoter
Sometimes requires rho(ρ) to terminate
Inhibited by rifampin, Actinomycin D

Eukaryotic RNA Polymerase

1. RNAP 1: rRNA (nucleolus). Except 5S rRNA

RNAP 2: hnRNA/mRNA and some snRNA

RNAP 3: tRNA,, 5S rRNA

2. No sigma, but transcription factors (TFIID) bind before RNA polymerase.

3. No rho required

4. RNAP2 inhibited by α- amanitin (mushrooms). Actinomycin D.