This document summarizes the process of transcription in bacteria. It defines transcription as the synthesis of RNA using a DNA template. There are three main classes of RNA - mRNA, rRNA and tRNA. Transcription requires a promoter, structural gene, terminator, RNA polymerase and other factors. RNA polymerase moves along DNA in the 5'-3' direction synthesizing RNA in the 3'-5' direction using complementary base pairing. Transcription includes initiation, elongation and termination steps. Termination can be rho-independent involving a hairpin loop or rho-dependent using a rho termination factor.

1. BIOSYNTHESIS OF RNA
( Transcription )
By
Ms.SHWETA DHUMALE (Bsc III)
Department of Microbiology
Willingdon College, Sangli
Maharashtra ,India

2. CENTRAL DOGMA
● “Central dogma is the process by which the
instructions in DNA are converted into a
functional product “
● The concept was given by Watson and crick

3. ● Structure of RNA &DNA
.

4. ● Three Major classes of RNA
These all three types of cellular RNA’s are copied during
Transcription
1.mRNA : ( Messenger RNA) carries the message from the DNA to
ribosome
2.rRNA : ( Ribosomal RNA) these are major structural components
of the protein Synthesizing ribosome.
3.tRNA : ( Transfer RNA ) read the information encoded in the
mRNA and transfer the appropriate amino acid to a growing
polypeptide chain during protien Synthesis

5. TRANSCRIPTION
Definition :
“ The process of Synthesizing RNA from the genetic
information encoded by DNA is called as Transcription”
OR
“Transcriptions is the process by which RNA is built from a
template of DNA”

6. ● Transcription Requirment
1. Promoter
2. Structural Gene
3. Terminator
4. Initiation factor
5. Terminator factor
6. RNA Polymerase

7. ● PROMOTER :
● It is the small sequence of DNA
which provides binding site for RNA
Polymerase.
● It present at 5’ end.
● Also called as upstream end.

8. ● TERMINATOR :
● It is small sequence of DNA which
provides binding site for Terminator
factor.
● It presents at 3’ end.
● Also called as Downstream end.

9. ● STRUCTURAL GENE :
● These are the gene to be transcribed.
● Structural gene in prokaryotic cell is
polycistronic.
● Structural gene in eukaryotic cell is
monocistronic.

10. ● INTIATION FACTOR :
● For Transcription the initiation
factor is Sigma (σ).

11. ● TERMINATOR FACTOR
:
● The Factor terminating the process
of Transcription is Rho.

12. ● RNA Polymerase
“RNA Polymerase is an enzyme that is responsible for copying a DNA
sequence into RNA sequence, during the process of Transcription”
● The enzyme responsible for RNA Synthesis is DNA -dependant
RNA Polymerase.
● The prokaryotic RNA Polymerase is a multiple subunit protein of
~480kD.
● Eukaryotic systems have three kinds of RNA Polymerase, each of
which is a multiple subunit protein and responsible for Transcription
of different RNAs.

13. ● Salient features of Transcription
● Synthesis of all types of RNA in Nucleus
● Only one strand of DNA is praticipates
● Ribonucleotides are used in RNA Synthesis
● RNA Synthesis occurs in 5’-3’
direction,DNA template is read from 3’-5’
direction
● Synthesis follows Watson-Crick base pairing
rules - A to U , G to C

14. .

15. ● Transcription in Prokaryotes
● Transcription is catalyzed by RNA Polymerase enzyme
which makes RNA using DNA as a template
● The strands of DNA which is transcribed is the
template/non-coding/sense strands in 3’-5’ direction
● The other strands is called non-sense/non-
template/coding strands which is in 5’-3’ direction
● Prokaryotes have only one RNA Polymerase which
Synthesis all the three types of RNAs

16. .
● RNA Polymerase moves
along the template strand
of DNA in the 5’-3’
direction.
● RNA Polymerase consist of
5 polypeptide chains 2α , β
, β’ and σ.
● The σ subunit recognizes
promoter on DNA template
● β subunit helps in
formation of
phosphodiester bond.
● β’ subunit helps in binding
with template DNA.

17. ● Steps Involved in Transcription:
●INITIATION
●ELONGATION
●TERMINATION

18. ●INITIATION :
● Transcription factor
recognize the promoter
(TATA box) & bind to it.
● RNA Polymerase follow
Transcription factor in
binding DNA.
● Formation of the
Transcription initiation
complex.
● Unwinding of DNA double
helix.
● RNA Synthesis begins.

19. ●ELONGATION :
● RNA Polymerase moves
along the DNA template
strand.
● Complementary RNA
nucleotides are added to
the 3’end.
● RNA peels away and DNA
double helix reforms.

20. ●TERMINATION
● Rho Independent
● Rho Dependant

21. ● Rho Independent termination:
● The newly formed RNA
has GC rich sequence
followed by Poly U
sequence.
● GC rich sequence form
hairpin loop which
pulls RNA chain &
weak bond between
A=U broken & RNA is
released.

22. ● Rho Dependant termination :
● Rho factor/ protein causes
disruption of RNA- DNA
hybrid.
● Rho protein is a specialized
helical which recognize 50-
90 bp upstream of
Terminator in mRNA
sequence.
● Rho protein releases newly
formed RNA.

23. Thank you !!!