1. Molecular Biology – Transcription
Dr Anurag Yadav
Department of Biochemistry
Instagram page –biochem365
YouTube – Dr Biochem365
MNR MEDICAL COLLEGE & HOSPITAL
4. • The conventional concept of central dogma of
life which is essence .
• DNA makes RNA makes Protein.
• Total DNA contained in an organism or a cell is
regarded as the genome.
• Genomics: The study of structure and function
• The RNA copies of the active protein coding
genes represent transcriptome.
• The Study of transcriptome that involves all
the RNA molecules made by a cell, tissue or an
organism is transcriptomics.
• Study of proteome is proteomics.
• Metabolomics: the use of genome sequence
analysis for determining the capability of a
cell, tissue or an organism to synthesize small
molecules (metabolites) is metabolomics.
• Transcription is a process in which ribonucleic
acid (RNA) is synthesized from DNA.
• The word gene refers to the functional unit of
• Genetic information stored in DNA is
expressed through RNA.
9. • One of two strand of DNA serves as a
template (non coding or antisense strand) and
produces working copies of RNA molecules.
• The other strand which does not participate in
transcription is referred to as coding strand or
sense strand or non-template strand.
11. TRANSCRIPTION IS SELECTIVE
• The entire molecule of DNA is not expressed
• RNAs are synthesized only for some selected
region of DNA.
• The identification of the specific region on
DNA is inbuilt.
12. • The product formed in transcription is referred
to as primary transcript.
• Most of the time they are inactive.
• Activated with alteration – post-
transcriptional modification. (Functional RNA
13. TRANSCRIPTION IN PROKARYOTES
• RNA polymerase: DNA dependent RNA
polymerase – synthesizes all the RNAs.
• Complex holoenzyme – 5 polypeptide
subunits - 2α, 1β and 1β’ and one sigma(s)
• The enzyme without sigma factor is referred
to as core enzyme.
16. 1. INITIATION
• RNA Polymerase to DNA : is Prerequisite.
• Promoter Region : Specific region on the DNA
where the enzyme binds.
• Two base sequence on the coding DNA strand.
• Sigma factor of RNA: recognise for initiation.
17. Pribnow Box (TATA Box):
• 6 nucleotide bases (TATAAT), located on
left side of 10 bases away (upstream from
starting point of transcription.
The ‘-35’ sequence:
• second recognition site in promoter
region of DNA. Contain TTGACA – located
35bases (Upstream) away from left side
from the site of transcription start.
20. 2. ELONGATION
• Promoter is recognised, sigma factor is
released and transcription proceeds.
• RNA synthesized from 5’ end to 3’ end
antiparallel to the DNA template.
• The sequence of Nucleotide bases is
complementary to template DNA strand.
21. RNA Polymerase:
• No primer is required.
• Does not possess endo or exonuclease
• Hence, there is no ability to repair the mistake
in the RNA synthesized.
24. 1. Rho (ρ) Dependent termination
• ρ factor, bind to growing part of RNA or DNA.
• Acts as ATPase and terminated transcription
and release RNA.
• Also responsible for the dissociation of RNA
polymerase from DNA.
26. 2. Rho (ρ) Independent termination
• The termination in this case is brought about by
the formation of hairpins of newly synthesized
• This occur due to presence of palindromes.
• Palindrome: is word that reads alike forward and
– Eg: madam, rotor.
28. • Much more complicated.
• All the eukaryotic transcription are not clearly
TRANSCRIPTION IN EUKARYOTES
29. RNA Polymerases
• Synthesis precursor for large
• Synthesize precursor for
mRNAs and small nuclear RNAs
• Formation of tRNAs and small
30. Promoter sites
Hogness box (TATA box)
• Located left about 25 nucleotides (Upstream).
• between 70-80 nucleotides upstream from the start of
These two will help RNA polymerase II to recognize
the requisite sequence of DNA for transcription.
CHROMATIN combining the promoter
Binding of transcription factors (TFs) to
DNA sequences in the promoter region.
Stimulation of transcription by enhancers.
• It increase gene expression by 100 folds.
• Binding of enhancer to transcription factors to
• It is believed that chromatin forms a loop that
allows the promoter and enhancer to be close
together in space to facilitate transcription.
36. HETEROGENEOUS NUCLEAR RNA
• The primary mRNA transcript produced by
RNA polymerase II in eukaryotes is often
referred to as heterogeneous nuclear RNA
• This is then processed to produce mRNA
needed for protein synthesis.
39. 1. The 5’ capping
• 5’ end of mRNA is capped with 7-
methylguanosine by unusual 5’ to 5’
• It is required for translation process.
• Stabilizing the structure of mRNA
40. 2. Poly-A tail
• Adenine nucleotide chain is added at 3’ end.
• Stabilize the mRNA
41. 3. Introns and their Removal
• Introns are intervening nucleotide sequence.
• They do not code for Proteins
• Exons of mRNA possess the genetic code for
• This removal of Introns is promoted by small
nuclear ribonucleo-protein particles (snRNPs).
• They are produced in association with small
nuclear RNA .
42. • Spliceosome : snRNP association with hnRNA
at exon-intron junction.
• This is than, mature RNA enters the cytosol.
46. Faulty splicing can cause diseases
• Performed with precision to produced the
• Faulty will lead to disease / disorders.
• Eg: β-thalassemia.
• Mutation resulting in nucleotide change at an
• Result in diminished or lack of synthesis of β-
chain of hemoglobin.