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.
Eukaryotic DNA replication is a conserved mechanism that restricts DNA replication to once per cell cycle. Eukaryotic DNA replication of chromosomal DNA is central for the duplication of a cell and is necessary for the maintenance of the eukaryotic genome.
DNA replication in eukaryotes occurs in three stages: initiation, elongation, and termination, which are aided by several enzymes. Because eukaryotic genomes are quite
complex, DNA replication is a very complicated process that involves several enzymes and other proteins. It occurs in three main stages: initiation, elongation, and termination.
DNA replication is the most important process central dogma in the molecular genetics. So i hope this power point presentation useful to the students of B.Sc Agriculture and M.Sc Genetics and Plant Breeding.
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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.
Eukaryotic DNA replication is a conserved mechanism that restricts DNA replication to once per cell cycle. Eukaryotic DNA replication of chromosomal DNA is central for the duplication of a cell and is necessary for the maintenance of the eukaryotic genome.
DNA replication in eukaryotes occurs in three stages: initiation, elongation, and termination, which are aided by several enzymes. Because eukaryotic genomes are quite
complex, DNA replication is a very complicated process that involves several enzymes and other proteins. It occurs in three main stages: initiation, elongation, and termination.
DNA replication is the most important process central dogma in the molecular genetics. So i hope this power point presentation useful to the students of B.Sc Agriculture and M.Sc Genetics and Plant Breeding.
Instructions for Submissions thorugh G- Classroom.pptxJheel Barad
This presentation provides a briefing on how to upload submissions and documents in Google Classroom. It was prepared as part of an orientation for new Sainik School in-service teacher trainees. As a training officer, my goal is to ensure that you are comfortable and proficient with this essential tool for managing assignments and fostering student engagement.
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The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
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Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
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http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
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3. CONTENTS
What is DNA REPLICATION ?
Structure of DNA
Meselson & stahl’s Experiment.
Separation of DNA by Centrifugation.
What is DNA Replication ?
What is the role of enzymes in DNA REPLICATION ?
Steps of DNA Replication
DNA Replication in prokaryotes and Eukaryotes
4. What is DNA?
Deoxyribonucleic acid (DNA) is a nucleic
acid that is made up of three components:
a deoxyribose sugar, a phosphate, and a
nitrogenous base.
DNA is the genetic material via which a
cell is defined. It is a long molecule
containing unique codes that give
instructions for the synthesis of all body
proteins.
5. STRUCTURE OF DNA
The structural model of DNA was initially proposed by James Watson and Francis
Click.
They found that DNA is a double-helical structure with two paired DNA strands
with complementary nucleotide sequences.
DNA is made up of millions of nucleotides. Nucleotides are molecules that are
composed of deoxyribose sugar, with a phosphate group and a nucleobase that is
attached to it.
Each nucleotide is tightly base paired with a complementary nucleotide on the
opposite strand, i.e. Adenine (A) paired with Thymine (T) or Guanine (G) paired
with cytosine (C), and therefore one strand’s sequence acts as a template for the
new strand to be formed during replication.
Nucleotides are bound to each other in strands via phosphodiester bonds forming a
sugar-phosphate backbone.
They form a bond that is between the third carbon atom on the deoxyribose sugar
made up of one sugar thus it is designated as the 3′ (three prime) and the fifth
carbon atom of another sugar on the next nucleotide as the 5′ (five prime).
7. Meselson and Stahl Experiment
Meselson and Stahl Experiment was an experimental proof for
semiconservative DNA replication.
Matthew Meselson and Franklin stahl in 1958 performed experiment on E
coli to prove that DNA replication is semi-conservative .
1. EXPERIMENT
Meselson and Stahl grew E.coli on a medium that contains 15NH4Cl as the
only nitrogen source for many generations [Note: 15N is the heavy isotope
of nitrogen]. As a result, all newly synthesized DNA had 15N which can be
differentiated from normal DNA by centrifugation in a caesium chloride
(CsCl) density gradient.
They then transferred the cells to a medium containing normal 14NH4Cl.
As the cells multiplied, they collected samples at time intervals (20mins,
40mins, 60mins etc.). This is because E. Coli cells divide every 20
minutes. They then extracted the double-stranded DNA from the samples
and separated them on CsCl gradients to measure the DNA densities.
10. RESULT
DNA extracted after 20 minutes (one generation) in the
14NH4Cl medium had an intermediate density. This is
because it contained one parental DNA strand with the
heavy 15N and one new DNA strand with the light 14N to
give 15N14N.
DNA extracted after 40 minutes (two generations) in the
14NH4Cl medium showed equal amounts of intermediate
density and light density. This is because it contained
equal amounts of the hybrid 15N14N DNA (intermediate)
and 14N14N DNA (light).
11. CONCLUSION
Based on observations and experimental results,
Meselson and Stahl concluded that DNA molecules
can replicate semi-conservatively. Investigation of
semi-conservative nature of replication of DNA or
the copying of the cells, DNA didn’t end there.
Followed by Meselson and Stahl experiment, Taylor
and colleagues conducted another experiment on
Vicia faba (fava beans) which again proved that
replication of DNA is semi-conservative.
12. What is DNA Replication?
This is a complex process that takes place during cell division, (interphase, S phase)
whereby DNA makes copies (duplicates) before the cell divides through mitosis and
meiosis.
DNA replication is a semiconservative process where a parental strand (template) is
used to synthesize a new complementary daughter strand using several protein
elements which include enzymes and RNA molecules.
DNA replication process uses DNA polymerase as the main enzyme for catalysing the
joining of deoxyribonucleoside 5′-triphosphates (dNTPs) forming a growing chain of
DNA.
Other proteins are also involved for initiation of the process and copying of DNA, along
with proofreading capabilities to ensure the replication process takes place accurately.
Therefore DNA replication is a process that produces identical helices of DNA from a
single strand of the DNA molecule.
DNA replication is an essential mechanism in enhancing cell growth, repair, and
reproduction of an organism.
13.
14. Role of Enzymes in DNA Replication
DNA replication is a highly enzyme-dependent
process. There are many enzymes involved in
DNA replication, which includes the enzymes,
DNA-dependent DNA polymerase, helicase,
ligase, etc. Among them, DNA-dependent
DNA polymerase is the main enzyme.
15. DNA-dependent DNA polymerase
It helps in the polymerisation, catalyses and regularises the whole process
of DNA replication with the support of other enzymes.
Deoxyribonucleoside triphosphates are the substrate as well as the energy
provider for the replication process. DNA polymerase is of three types:
1.DNA Polymerase I
It is a DNA repair enzyme. It is involved in three activities:
5′-3′ polymerase activity
5′-3′ exonuclease activity
3′-5′ exonuclease activity .
2.DNA Polymerase II
It is responsible for primer extension and proofreading.
3.DNA Polymerase III
It is responsible for in vivo DNA replication.
16. Helicase
helicase is the enzyme, which unzips the DNA strands by breaking the hydrogen
bonds between them. Thus, it helps in the formation of the replication fork.
Ligase
Ligase is the enzyme which joins together the Okazaki fragments of the
discontinuous DNA strands.
Primase
This enzyme helps in the synthesis of RNA primer complementary to the
DNA template strand.
Endonucleases
These produce a single-stranded or a double-stranded cut in a DNA
molecule.
Single-stranded Binding Proteins
It binds to single-stranded DNA and protects it from forming secondary
structures.
17. DNA REPLICATION STEPS
1. Initiation
DNA replication demands a high degree of accuracy because even a minute
mistake would result in mutations. Thus, replication cannot initiate
randomly at any point in DNA.
For the replication to begin there is a particular region called the origin of
replication. This is the point where the replication originates. Replication
begins with the spotting of this origin followed by the unwinding of the
two DNA strands.
Unzipping of DNA strands in their entire length is not feasible due to high
energy input. Hence, first, a replication fork is created catalysed by the
helicase enzyme, which unzips the DNA strand.
18. 2.ELONGATION
As the strands are separated, the polymerase enzymes start synthesising the
complementary sequence in each of the strands. The parental strands will act
as a template for newly synthesising daughter strands.
It is to be noted that elongation is unidirectional i.e. DNA is always
polymerised only in the 5′ to 3′ direction.
Therefore, in one strand (the template 3‘→5‘) it is continuous, hence called
continuous replication while on the other strand (the template 5‘→3‘) it is
discontinuous replication.
They occur as fragments called Okazaki fragments. The enzyme called DNA
ligase joins them later.
20. 3.TERMINATION
Termination of replication occurs in different ways in different organisms. In
E.coli like organisms, chromosomes are circular. And this happens when the
two replication forks between the two terminals meet each other.
21.
22.
23.
24.
25. DNA Replication Process in Prokaryotes
The DNA replication in prokaryotes takes place in the following place:
1. The two strands of DNA unwind at the origin of replication.
2. Helicase opens the DNA and replication forks are formed.
3. The DNA is coated by the single-strand binding proteins around the replication
fork to prevent rewinding of DNA.
4. Topoisomerase prevents the supercoiling of DNA.
5. RNA primers are synthesised by primase. These primers are complementary to
the DNA strand.
6. DNA polymerase III starts adding nucleotides at the end of the primers.
7. The leading and lagging strands continue to elongate.
8. The primers are removed and the gaps are filled with DNA Polymerase I and
sealed by ligase.
26. DNA Replication in Eukaryotes
The DNA replication in eukaryotes is
similar to the DNA replication in
prokaryotes. However, the initiation
process is more complex in eukaryotes
than prokaryotes. In eukaryotes, there
are multiple origins of replication
present. A pre-replication complex is
made with other initiator proteins. The
process is entirely the same but the
enzymes used are different. E.g. In
eukaryotes, the polymerisation process
is carried out by the enzyme Pol δ,
whereas in prokaryotes it is done by
DNA Pol III.
27. THE END
🙏🙏THANK YOU ALL🙏🙏
Made By : T.Ramyasri
Bsc 2nd year (Life Science )
subject : BIOTECHNOLOGY
Roll. No : 110121342005
