Transcription is the first step in gene expression, involving RNA polymerases that synthesize RNA from a DNA template in three stages: initiation, elongation, and termination. Prokaryotic transcription is simpler and occurs in the cytoplasm, while eukaryotic transcription is more complex, taking place in the nucleus and involving pre-mRNA processing. Key differences between prokaryotic and eukaryotic transcription include the number of RNA polymerases, promoter recognition, and post-transcriptional modifications such as splicing and capping.

2. • Transcription is the first step in gene expression.
• Transcription is the process performed by enzymes called RNA
polymerases, which link ribonucleotides to form an RNA strand
using one of DNA strand having 3-5 prime direction called
template strand).
• Transcription has three stages
1. Initiation
2. Elongation
3. Termination.

3. 1. In prokaryotes the transcription is simple while in eukaryotes the
transcription is complicated or complex.
2. Occurrences
Prokaryotic transcription occurs in cytoplasm.
Eukaryotic transcription occurs in nucleus.
3. In prokaryotes mRNA is transcribed directly from the template
DNA strand while in eukaryotes 1st pre-mRNA is formed and then
processed to yield mature mRNA.

4. 4. RNA polymerase numbers and subunit
Prokaryotes = Only one RNA pol having 5 subunit i.e. 2 alpha and
beta while one omega subunit while involved in synthesizing
mRNA, tRNA and rRNA.
Eukaryotes= Three RNA polymerase i.e RNA polymerase 1,2,and 3.
RNA pol 1 have 14 subunit and synthesize rRNA.
RNA pol 2 have 10-12 subunit and synthesize mRNA.
RNA pol 3 have 12 subunit and synthesize tRNA.

5. 5. Promoters in prokaryotes and eukaryotes
transcription
During transcription in prokaryotes the RNA polymerase
recognize and bind to the promoter region with the help of
sigma factor that are located to upstream of the start site and
contain prinbow box (TATAAT) at -10 position while in
eukaryotes 1st the promoter region is occupied by
transcription IF and then RNA polymerase bind. The promoter
region contain TATA box at -30, CAT box at -80 and GC box
at -90 position.
6. Transcription termination
In prokaryotes termination of transcription is done by rho dependent
or independent mechanisms while in eukaryotes termination of
transcription will be done by termination sequence in DNA.

6. 7. Post transcriptional modification is not occur in prokaryotes
while in eukaryotes its occur after mRNA formed i. 5 prime
capping and 3 prime poly adinylation.
8. Splicing
Prokaryotes = Absent
Eukaryotes = Once mRNA is formed then all introns portion are
removed while exons are just remain and rejoin with each other
through splisosome