DNA transcription is a process that involves transcribing genetic information from DNA to RNA. The transcribed DNA message, or RNA transcript, is used to produce proteins. DNA is housed within the nucleus of our cells. It controls cellular activity by coding for the production of proteins. The information in DNA is not directly converted into proteins, but must first be copied into RNA. This ensures that the information contained within the DNA does not become tainted.
The flow of information in the cell starts at DNA, which replicates to form more DNA. Information is then ‘transcribed” into RNA, and then it is “translated” into protein.
Information does not flow in the other direction.
A few exceptions to the Central Dogma exist
some RNA viruses, called “retroviruses”.
This Powerpoint consists of RNA synthesis (transcription) in prokaryotes and eukaryotes. This also explains about the post-transcriptional modifications in the mRNA. How the post transcriptionla modifications help in the gene expression.
The flow of information in the cell starts at DNA, which replicates to form more DNA. Information is then ‘transcribed” into RNA, and then it is “translated” into protein.
Information does not flow in the other direction.
A few exceptions to the Central Dogma exist
some RNA viruses, called “retroviruses”.
This Powerpoint consists of RNA synthesis (transcription) in prokaryotes and eukaryotes. This also explains about the post-transcriptional modifications in the mRNA. How the post transcriptionla modifications help in the gene expression.
Prokaryotes are organisms that consist of a single prokaryotic cell. Eukaryotic cells are found in plants, animals, fungi, and protists. They range from 10–100 μm in diameter, and their DNA is contained within a membrane-bound nucleus.Prokaryotes do not have membrane-enclosed nuclei. Therefore, the processes of transcription, translation, and mRNA degradation can all occur simultaneously.
description of mechanism of transcription in prokaryotes and eukaryotes with clear explanation and clear pictures and also mentiong of different promotors and enhancers and silencers
This presentation explains DNA transcription and RNA Processing.
It gives details about prokaryotic DNA transcription and eukaryotic DNA transcription. it also explains post-transcriptional modification both in prokaryotes and eukaryotes.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Prokaryotes are organisms that consist of a single prokaryotic cell. Eukaryotic cells are found in plants, animals, fungi, and protists. They range from 10–100 μm in diameter, and their DNA is contained within a membrane-bound nucleus.Prokaryotes do not have membrane-enclosed nuclei. Therefore, the processes of transcription, translation, and mRNA degradation can all occur simultaneously.
description of mechanism of transcription in prokaryotes and eukaryotes with clear explanation and clear pictures and also mentiong of different promotors and enhancers and silencers
This presentation explains DNA transcription and RNA Processing.
It gives details about prokaryotic DNA transcription and eukaryotic DNA transcription. it also explains post-transcriptional modification both in prokaryotes and eukaryotes.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
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Monitor common gases, weather parameters, particulates.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Richard's entangled aventures in wonderlandRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
2. Three Different Classes of RNA
1) rRNA (ribosomal)
• large (long) RNA molecules
• structural and functional components of
ribosomes
• highly abundant
2) mRNA (messenger)
• typically small (short)
• encode proteins
• multiple types, not abundant
3) tRNA (transfer) and small ribosomal RNAs
• very small
• Important in translation
Not all genes encode proteins
3. In Bacteria
- all three classes are transcribed by the
same RNA polymerase
In Eukaryotes
- each class is transcribed by a different
RNA Polymerase
•RNAP I - rRNAs
•RNAP II - mRNAs
•RNAP III - tRNAs & small ribosomal
RNAs
Different Types of RNA Polymerase
6. •Promoters
- DNA sequences that guide RNAP to the beginning of
a gene (transcription initiation site).
•Terminators
- DNA sequences that specify then termination of RNA
synthesis and release of RNAP from the DNA.
•RNA Polymerase (RNAP)
- Enzyme for synthesis of RNA.
•Steps
• 1) Initiation.
2) Elongation.
3) Termination.
Bacterial (Prokaryotic) Transcription
7. -10 region
RNAP binds a region of DNA from -40 to +20
The sequence of the non-template strand is shown
TTGACA…16-19 bp... TATAAT
“-35” spacer “-10”
8. Important Promoter Features
• The closer the match to the consensus the stronger the
promoter (-10 and -35 boxes)
• The absolute sequence of the spacer region (between
the -10 and -35 boxes) is not important
• The length of the spacer sequence IS important:
TTGACA - spacer (16 to 19 base pairs) - TATAAT
• Spacers that are longer or shorter than the consensus
length make weak promoters
9. Properties of Promoters
• Promoters typically consist of a 40 bp
region on the 5'-side of the transcription
start site
• Two consensus sequence elements:
– The "-35 region", with consensus TTGACA
– The Pribnow box near -10, with consensus
TATAAT - this region is ideal for unwinding.
10. RNA Polymerase Has Many Functions
• Scan DNA and identify promoters
• Bind to promoters
• Initiate transcription
• Elongate the RNA chain
• Terminate transcription
• Be responsive to regulatory proteins
(activators and repressors)
Thus, RNAP is a multisubunit enzyme
11. Transcription in Prokaryotes
• In E.coli, RNA polymerase is a 465 kD complex, with
2 , 1 , 1 ', 1 (holoenzyme).
• Core enzyme is 2 , 1 , 1 ’ (can transcribe but it
can’t find promoters).
• recognizes promoter sequences on DNA; ' binds
DNA; binds NTPs and interacts with .
subunits appear to be essential for assembly and for
activation of enzyme by regulatory proteins.
13. I
’
II
70
RNAP HOLOENZYME -70
Promoter-specific
transcription initiation
In the Holoenzyme:
· ' binds DNA
· binds NTPs
· and ' together make up the active site
· subunits appear to be essential for assembly and
for activation of enzyme by regulatory proteins. They
also bind DNA.
· recognizes promoter sequences on DNA
14. Binding of polymerase to Template DNA
• Polymerase binds nonspecifically to DNA with
low affinity and migrates, looking for promoter.
• Sigma subunit recognizes promoter sequence.
• RNA polymerase holoenzyme and promoter
form "closed promoter complex" (DNA not
unwound).
• Polymerase unwinds about 12 base pairs (A-T
rich) to form "open promoter complex“.
15. Finding and binding
the promoter
Closed complex
formation
RNAP bound -40 to
+20
Open complex
formation
RNAP unwinds from -
10 to +2
Binding of 1st NTP
Requires high
purine [NTP]
Addition of next NTPs
Requires lower
purine [NTPs]
Dissociation of sigma
After RNA chain
is 6-10 NTPs long
16. Chain Elongation
Core polymerase - no sigma
• Polymerase is accurate - only about 1 error in
10,000 bases (not as accurate as DNAP III)
• Even this error rate negligible- since many
transcripts are made from each gene
• Elongation rate is 20-50 bases per second -
slower in G/C-rich regions and faster elsewhere
• Topoisomerases precede and follow polymerase
to relieve supercoiling
17. Two mechanisms
1. Rho dependent
Rho - the termination factor protein
An ATP-dependent helicase
– it moves along the RNA transcript, finds the
"bubble", unwinds it and releases the RNA
chain.
Chain Termination
20. Two mechanisms
2) Rho-Independent (Intrinsic)
- termination sites in DNA
– inverted repeat, rich in G:C, which forms a stem-
loop in RNA transcript
– 6-8 nos of A’s in DNA coding for U’s in transcript
Chain Termination
22. Rho-independent
transcription
termination
• RNAP pauses when it
reaches a termination site.
• The pause may give the
hairpin structure time to fold
• The fold disrupts important
interactions between the
RNAP and its RNA product
• The U-rich RNA can
dissociate from the template
• The complex is now
disrupted and elongation is
terminated
23. • Bacterial environment changes rapidly.
• Survival depends on ability to adapt.
• Bacteria must express the enzymes required
to survive in that environment.
• Enzyme synthesis is costly (energetically).
• So make enzymes only when required.
Transcription Regulation in Prokaryotes
Why is it necessary?
24. Proteins
Constitutive
• Always expressed
• “housekeeping”
• e.g. glucose metabolizing
enzymes
• Glucose is the preferred
carbon source for
bacteria
Adaptive
• “inducible”
• Made only when needed
• e.g. Lactose metabolizing
enzymes
• Made only if lactose is the
sole carbon source
• Not made if glucose is
present
25. 1. Alternate sigma factor usage: controls selective
transcription of entire sets of genes
s32
s60
vegetative
(principal s)
heat shock
nitrogen
starvation
s70
TTGACA TATAAT
(16-19 bp) (5-9 bp) A
+1
CNCTTGA CCCATNT
(13-15 bp) (5-9 bp) A
+1
CTGGNA TTGCA
(6 bp) (5-9 bp) A
+1
Ways to Regulate Transcription
26. 2. Positive Regulation (activation): a positive regulatory
factor (activator) improves the ability of RNAP to
bind to and initiate transcription at a weak promoter.
Ways to Regulate Transcription
RNAP
-35 -10 +1
Activator
Activator binding site
EXAMPLE: CAP
27. 3. Negative Regulation (repression): a negative regulatory
factor (repressor) blocks the ability of RNAP to
bind to and initiate transcription at a strong promoter.
Ways to Regulate Transcription
RNAP
-35 -10
Repressor
Operator
EXAMPLE: lac REPRESSOR
28. Protein Synthesis is Regulated
Transcriptionally
• Genes that encode proteins with related functions are
grouped into transcriptional units called “operons”
• This ensures that genes for enzymes in the same metabolic
pathway are all made at the same time
Operons have three functional “parts”
1) structural genes: these encode proteins
2) promoter
3) regulatory sequences that interact with regulatory proteins
Sometimes an operon is associated with:
4) regulatory genes: these encode proteins regulating expression
of that operon
29. Structural genes
promoter
Operator (regulatory
sequence that binds a
repressor protein)
Architecture of a typical operon
By regulating a single promoter you can co-ordinate the
expression of three genes (in this example)
RNA transcript covers all genes in the operon
= “polycistronic RNA”
31. RNA polymerases
– Much more complex than prokaryotic RNAP
a) RNAP I – synthesizes ribosomal RNA
b) RNAP II – synthesizes messenger RNA
c) RNAP III – synthesizes transfer RNA and 1 type
of rRNA
Eukaryotic RNAPs have subunits that are
homologous to a, b, and b’ of prokaryotic RNAP;
however, eukaryotic RNAP also contain many
additional subunits.
32. a. Initiation
• Transcription initiation needs promoter
and upstream regulatory regions.
• The cis-acting elements are the specific
sequences on the DNA template that
regulate the transcription of one or
more genes.
33. Eukaryotic promoters
• a) contain a TATA rich region located –25
to -30 from the start of transcription
• b) CCAAT (frequently at –75)
• c) GC box
• d) Some promoters have other sequences
located either upstream or downstream
that maximize the level of transcription
called enhancers
36. • RNA-pol does not bind the promoter
directly.
• RNA-pol II associates with six
transcription factors, TFII A - TFII H.
• The trans-acting factors are the
proteins that recognize and bind
directly or indirectly cis-acting
elements and regulate its activity.
Transcription factors
38. Assembly of RNA pol and transcription
factors at promoter
• Formation of closed complex –TATA binding
protein (TBP) binds to TATA box.
• TBP requires TFIIB
• TFIIA can stabilize TFIIB-TBP complex.
• To TFIIB-TBP complex binds another complex ,
TFIIF and Pol II.
• TFIIF helps target Pol II to promoters..
• TFIIE and TFIIH bind to form the closed complex.
• TFIIH has helicase activity- unwinds DNA
40. • TF II H is of protein kinase activity to
phosphorylate CTD of RNA-pol.
• (CTD is the C-terminal domain of RNA-pol)
• Only the p-RNA-pol can move toward the
downstream, starting the elongation phase.
• Most of the TFs fall off from PIC during the
elongation phase.
Phosphorylation of RNA-pol
41. • The elongation is similar to that of
prokaryotes.
• The transcription and translation do
not take place simultaneously since
they are separated by nuclear
membrane.
b. Elongation
42. • The termination sequence is AATAAA
followed by GT repeats.
• The termination is closely related to
the post-transcriptional modification.
c. Termination