DNA replication in prokaryotes involves unwinding the DNA double helix at the origin of replication by helicase. This forms replication forks where leading and lagging strands are synthesized. The leading strand is replicated continuously while the lagging strand forms Okazaki fragments which are later joined by ligase. Replication terminates when the replication forks meet at positions opposite to the origin. Key enzymes include DNA polymerase III, helicase, primase, and ligase.
DNA Replication In Eukaryotes (Bsc.Zoology)DebaPrakash2
This Slide Is explanation of Mechanism of DNA Replication In Eukaryotes.
As we know we all have DNA as the genetic material and So we should know how this DNA getting Duplicated so that it'll pass to daughter cells.
DNA Replication In Eukaryotes (Bsc.Zoology)DebaPrakash2
This Slide Is explanation of Mechanism of DNA Replication In Eukaryotes.
As we know we all have DNA as the genetic material and So we should know how this DNA getting Duplicated so that it'll pass to daughter cells.
Replication Introduction , DNA replicating Models , Meselson and Stahl Experiments , Circuler Model of DNA replication , Replication in Prokaryotes , Replication In Eukaryotes , Comparison Between Prokaryotes and Eukaryotes Replicaton and PCR (Polymerease Chain Reaction)
SOS response was discovered by Miroslav Radman. It's a part of DNA repair system- synthesizes enzymes required for DNA repair. Cellular response to UV damage.
Replication Introduction , DNA replicating Models , Meselson and Stahl Experiments , Circuler Model of DNA replication , Replication in Prokaryotes , Replication In Eukaryotes , Comparison Between Prokaryotes and Eukaryotes Replicaton and PCR (Polymerease Chain Reaction)
SOS response was discovered by Miroslav Radman. It's a part of DNA repair system- synthesizes enzymes required for DNA repair. Cellular response to UV damage.
The process by which DNA molecule makes its identical copies is known as DNA replication or DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule
DNA replication is fundamental process occurring in all living organism to copy their DNA. The process is called replication in sense that each strand of dsDNA serve as template for reproduction of complementary strand.
Replication:
DNA replication is the biological process of producing two identical copies of DNA from the original/parentral DNA molecule.
This process occurs in all living organism.
Basis for biological inheritance
DNA Replication Is Semiconservative
Replication Begins at an Origin and Usually Proceeds Bidirectionally
DNA Synthesis Proceeds in a 5’-3’ Direction and Is semidiscontinuous
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.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
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.
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 .
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.
2. Introduction
DNA replication is the biological process of
producing two identical replicas of DNA from
one original DNA molecule.
It is a biological process occurring in all living
organisms and it is the basis for biological
inheritance.
It is a semi-conservative process which was
proved by Meselson and Stahl.
3. Some general features of DNA
replication
The very first step in DNA replication is to
‘unzip’ the double helix structure of
the DNA molecule.
This is carried out by an enzyme called
“Helicase” which breaks the hydrogen
bonds holding the complementary bases of
DNA together (A with T, C with G).
4. Contd….
Helicase separates the DNA to form a
replication fork at the origin of replication
where DNA replication begins.
One of the strands is oriented in the 3’ to 5’
direction (towards the replication fork), this is
the leading strand. The other strand is
oriented in the 5’ to 3’ direction (away from the
replication fork), this is the lagging strand.
5. Contd….
Replication forks extend bi-directionally as
replication continues.
Okazaki fragments are formed on the lagging
strand, while the leading strand is replicated
continuously.
“DNA ligase” seals the gaps between the Okazaki
fragments.
Primase synthesizes an RNA primer with a free 3′-
OH, which DNA polymerase III uses to synthesize
the daughter strands.
6. Process of DNA replication
DNA replication completes in various steps:
1. Initiation: Replication begins at an “origin of
replication”
2. Elongation: New strands of DNA are
synthesized by DNA polymerase.
3. Termination: Replication is terminated
differently in prokaryotes and eukaryotes.
7. 1. Initiation:
The chromosome of a prokaryote is circular
molecule of DNA.
Replication begins at one origin of replication
and proceeds in both directions around the
chromosomes.
8. Contd….
The enzymes involved in the DNA replication are
closely associated in one large complex called
replisome .
The replisome consists of :
• The primosome – composed of primase and
helicase.
• DNA polymerase III molecules.
• Topoisomerase, ligase, SSB, initiator proteins.
9.
10. Activities take place in this
step:
The very beginning step of DNA replication is unwinding of
DNA molecules. This is done by the enzyme DNA helicase
which cause the two parent DNA strands to unwind and
separate from one another at the “origin of replication” to
form two Y- shaped replication forks.
“These replication forks are the actual site of DNA
copying”.
11. Contd….
After this, Helix destabilizing proteins binds to
the single stranded regions so that the two
strands do not rejoin.
Enzymes called topoisomerase produce breaks
in the DNA and then rejoins them in order to
relieve the stress in the helical molecule during
replication.
12. 2. Elongation :
Activities take place in this step:
In this phase, the synthesis of two new daughter
strand takes place complementary to the template
strand.
DNA polymerase III is the enzyme that
synthesizes the daughter strands.
At this point, a primer is needed so that DNA
polymerase III can begin to act.
This phase is marked by the synthesis of leading
strand and lagging strand.
13.
14. Contd….
Leading strand is synthesized continuously in
5’ to 3’ direction along the direction of the
movement of replication fork.
Lagging strand synthesis occurs
discontinuously by loop formation in short
segments called Okazaki fragments.
15. Contd….
The lagging strand is looped so that DNA synthesis
proceeds steadily on both the leading and lagging
strand templates at the same time.
The synthesis of Okazaki fragments on the lagging
strand requires DnaB helicase and DnaG primase
that constitute a functional unit within the replication
complex, the primosome.
DnaB helicase first unwinds the replication forks.
16. Contd….
DNA primase then associates with DnaB
helicase, which synthesizes a short RNA
primer.
The clamp loading complex of DNA pol III
loads a beta- sliding clamp to the primer.
The primer is then extended by the DNA pol
III, which completes the synthesis of one
Okazaki fragment.
17.
18. Contd….
Once an Okazaki fragment has been
completed, it’s RNA primer is removed and
replaced with DNA by DNA pol I, and the
remaining nick is sealed by DNA ligase.
DNA ligase catalyses the formation of
phosphodiester bond.
19. 3. TERMINATION
Activities take place in this step:
Replication of bacterial genome proceeds bi-
directionally which terminates at a position
diametrically opposite to the origin of
replication.
Replication terminates at the terminus region
containing multiple copies of a 20bp
sequence called Ter (terminus) sequences.
20. Contd….
Ter sequence works as a binding site for
protein Tus (terminus utilization substance)
which stops the DnaB helicase, resulting in
the termination of DNA replication.
The completed chromosomes then partitioned
into two daughter cells during cell division.
23. DNA POLYMERASE
DNA polymerase is an enzyme that carries out the
synthesis of a new strand on the template strand.
It is found in both prokaryotes and eukaryotes.
Three types of DNA polymerase takes part in
prokaryotic DNA replication, they are:
a) DNA polymerase I
b) DNA polymerase II
c) DNA polymerase III
24. DNA Polymerase I
It is the first DNA polymerase to be isolated
and purified.
DNA polymerase I has 5’- 3’ exonuclease
activity.
The 5’- 3’ exonuclease activity allows the
removal of ribonucleotides of the RNA primer,
utilized to initiate DNA synthesis.
The 5’- 3’ exonuclease activity is also utilized
during the repair of damaged DNA.
25. DNA Polymerase II
It has no 5’- 3’ exonuclease activity, rather it
has 3’- 5’ exonuclease activity.
The 3’- 5’ exonuclease function is utilized
during replication to allow DNA polymerase to
remove mismatched bases and is referred to
as the proof-reading activity of DNA
polymerase.
It is also utilized during the repair of damaged
DNA.
26. DNA Polymerase III
DNA polymerase III is the principle replication
enzyme required for DNA synthesis.
Prokaryotic DNA is replicated by DNA
polymerase III in the 5′ to 3′ direction at a rate
of 1000 nucleotides per second.
DNA polymerase III has very high processivity
and therefore, synthesizes DNA very quickly.
27. Conclusion
DNA replication is semi-conservative, with
each existing strand serving as a template for
the synthesis of a new strand.
Replication begins at, and proceeds bi-
directionally from the point of origin.
On one strand, synthesis is continous and on
the other strand the synthesis is discontinous.
28. Contd….
Okazaki fragments are joined together by
DNA ligase.
DNA polymerase III is the main replication
enzyme, DNA polymerase I is responsible
for special functions during replication and
repair.
Ter sequence works as the binding site for
protein Tus (terminus utilization substance)
which stops the DnaB helicase, resulting in
termination of DNA replication.
