DNA replication is the process by which a cell makes an identical copy of its DNA. It occurs during the S phase of the cell cycle and involves unwinding the DNA double helix, creating RNA primers, and synthesizing new DNA strands using existing strands as templates in the 5' to 3' direction. The replication factory contains many replication proteins that cluster together to duplicate DNA. Experimental evidence from Meselson-Stahl experiments supported the semi-conservative mode of replication, in which each new DNA molecule contains one original and one new strand. Replication initiates at specific origins of replication and proceeds bidirectionally.
There are slides about DNA replication and types of DNA.
Here we study about different enzymes of replication and its process.Places of enzyme action also shown in the slides.Different proteins are also discussed.
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)
There are slides about DNA replication and types of DNA.
Here we study about different enzymes of replication and its process.Places of enzyme action also shown in the slides.Different proteins are also discussed.
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)
DNA polymerases are a group of enzymes that are used to make copies of DNA templates, essentially used in DNA replication mechanisms. These enzymes make new copies of DNA from existing templates and also function by repairing the synthesized DNA to prevent mutations. DNA polymerase catalyzes the formation of the phosphodiester bond which makes up the backbone of DNA molecules. It uses a magnesium ion in catalytic activity to balance the charge from the phosphate group.
INTRODUCTION
HISTORY
ENZYMES AND PROTEINS INVOLVED
IN PROKARYOTIC DNA REPLICATION
DNA polymerases
Types and function
Additional enzymes
Helicase ,
SSBP,
Topoisomerase,
Primase ,
Ligase ,
Events and function of enzymes
CONCLUSION
REFERENCES
This presentation deals with DNA replication in mamalian mitochondria. Mammalian mtDNA is replicated by proteins distinct from those used for nuclear DNA replication. According to the strand displacement model, replication is initiated from two distinct origins, OH and OL.
This presentation is about the transcription machinery that is required for the transcription in eukaryotes. The comparison between the transcription factors involved in prokaryotes and eukaryotes. The initiation of transcription and how it helps in producing a mRNA.
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.
Eukaryotic transcription is the elaborate process that eukaryotic cells use to copy genetic information stored in DNA into units of RNA replica.- Source: Wikipedia
DNA polymerases are a group of enzymes that are used to make copies of DNA templates, essentially used in DNA replication mechanisms. These enzymes make new copies of DNA from existing templates and also function by repairing the synthesized DNA to prevent mutations. DNA polymerase catalyzes the formation of the phosphodiester bond which makes up the backbone of DNA molecules. It uses a magnesium ion in catalytic activity to balance the charge from the phosphate group.
INTRODUCTION
HISTORY
ENZYMES AND PROTEINS INVOLVED
IN PROKARYOTIC DNA REPLICATION
DNA polymerases
Types and function
Additional enzymes
Helicase ,
SSBP,
Topoisomerase,
Primase ,
Ligase ,
Events and function of enzymes
CONCLUSION
REFERENCES
This presentation deals with DNA replication in mamalian mitochondria. Mammalian mtDNA is replicated by proteins distinct from those used for nuclear DNA replication. According to the strand displacement model, replication is initiated from two distinct origins, OH and OL.
This presentation is about the transcription machinery that is required for the transcription in eukaryotes. The comparison between the transcription factors involved in prokaryotes and eukaryotes. The initiation of transcription and how it helps in producing a mRNA.
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.
Eukaryotic transcription is the elaborate process that eukaryotic cells use to copy genetic information stored in DNA into units of RNA replica.- Source: Wikipedia
The genetic material must produce a large number of copies of itself during the life cycle of an organism. The process by which a DNA molecule makes its identical copies is called DNA replication. The DNA molecule that undergoes replication may be termed as ‘parent molecule or template molecule, while the two molecules produced by replication may be called progeny molecules or daughter molecules.
Prokaryotic dna replication by kk sahuKAUSHAL SAHU
INTRODUCTION
HISTORY
TYPES OF DNA REPLICATION
ENZYMES AND PROTEINS INVOLVED
IN PROKARYOTIC DNA REPLICATION
MECHANISM OF PROKARYOTIC DNA
REPLICATION
INITIATION
ELONGATION
TERMINATION
CONCLUSION
REFERENCES
The presentation covers the details of DNA replication starting from the basics of the replication process to the chemistry of DNA synthesis as well as the different models of replication.
This Power Point Presentation entitled " Cytological Methods" explains steps in preparation of cytological slides to study mitosis in higher plants with the help of root tips procured from onion and garlic bulb and germinating seeds and also to study mitosis a in Charophytes as Chara and Nitella. Also describes meiotic preparations .
This Power point presentation entitled “Micrometry and Karyotype analysis” consists of 38 slides. Describes what is micromeasurement, type of micrometers,caliberation of ocular micrometer and measurement of microscopic objects as cells,chromosomes etc . Karyotype features as Total length of individual chromosome, centromeric index, Average chromosome length,Total chromatin Length and volume,TF%,Karyotype category as per Stebbins (1971),Karyotype Formula,Idiogram etc .
This power point presentation consisting of 41 slides is an attempt to describe what is photorespiration,major photorespiratory pathway in C3 plants ,why photorespiration doesnot take place in C4 plants,structure of Rubisco enzyme ,difference between Photorespiration and Dark respiration and Significance of Photorespiration
Structure and functions of MitochondriaICHHA PURAK
This Power Point Presentation (PPT) entitled “Structure and Functions of Mitochondria” consists of 118 slides with following sub-heads
INTRODUCTION
HISTORY
ORIGIN AND EVOLUTION OF MITOCHONDRIA
SYNTHESIS OF MITOCHONDRIA
ISOLATION OF MITOCHNDRIA
SHAPE , SIZE AND NUMBER OF MITOCHONDRIA
STRUCTURE OF MITOCHONDRIA
CHEMICAL COMPOSITION OF MITOCHONDRIA
FUNCTIONS OF MITOCHONDRIA
MITOCHONDRIA –POWER HOUSE OF CELL
MITOCHONDRIAL DNA/ GENOME
TRANSPORT OF PROTEINS INTO MITOCHONDRIA
MITOCHONDRIAL INHERITANCE
MITOCHONDRIAL DISEASES IN HUMAN
SUMMARY
QUESTIONS
BOOKS CONSULTED
REFERENCES
This Power Point Presentation (PPT) entitled “ Structure and Function of Lysosome”includes 43 slides with following sub- heads.
DEFINITION
INTRODUCTION/ STRUCTURE OF LYSOSOME
DISCOVERY OF LYSOSOME
DISTRIBUTION/LOCATION OF LYSOSOME
ORIGIN/ SYNTHESIS OF LYSOSOME
SHAPE AND SIZE OF LYSOSOME
CHEMICAL COMPOSITION OF LYSOSOME
LYSOSOMES ARE KNOWN AS SUICIDE BAGS
HOW THE CELL IS PROTECTED FROM LYSOSOME RUPTURE
COMMON FUNCTION OF LYSOSOME
TYPES OF LYSOSOME
DISORDERS IN HUMAN RELATED WITH LYSOSOME
SUMMARY
QUESTIONS
BOOKS CONSULTED
REFERENCES
This PPT consists of 15 slides only explaining Pleiotropy. This is a phenomenon when one gene controls more than one trait , the traits may be related .Generally one gene's product acts for many reactions and so can affect more than one trait. Examples can be seen in pea Coloured flower and pigmentation in leaf axil, frizzle trait in chicken, fur colour and deafness in cats,Human pleiotropic traits are PKU,Sickle cell Anaemia. HOsyndrome , p53 gene etc
This PPT consists of 24 slides explaining Polygenic Inheritance . Some traits are controlled by two or more genes. These traits differ from Mendelian traits and donot show discrete alternative or contrasting forms and show continuous ranges. Examples of such traits are wheat seed colour, plant height, Human skin colour controlled by at least three genes showing many shades of dark and fare, human height, human eye colour etc
Structure and functon of golgi apparatusICHHA PURAK
The Power point presentation consists of 77 slides including following heads
Introduction
Discovery
Distribution
Origin
Shape
Chemical composition
Structure
Common functions
Cell specific functions
Proteoglycans are assembled in G A
Lpid metabolism in G A
Protein sorting
Vesicular Tubular Clusters (VTCs)
Only properly folded and assembled protein can leave ER
Proteins leave ER in COPII coated transport vesicles
summary
questions
References
Structure and functions of endoplasmic reticulumICHHA PURAK
The presentation consists of 57 slides,describes following heads
• DISCOVERY
• INTRODUCTION
• BIOGENESIS OF ER
• ISOLATION OF MICROSOMES FROM E R
• STRUCTURE
• COMPONENTS OF ER
CISTERNAE
VESICLES
TUBULES
• MAIN FUNCTION OF ER
• TYPES OF ENDOPLASMIC RETICULUM
• SMOOTH ENDOPLASMIC RETICULUM (SER)
• FUNCTIONS OF SER
• ROUGH ENDOPLASMIC RETICULUM (RER)
• FUNCTIONS OF RER
• SUMMARY
• REFERENCES
• QUESTIONS
Structure and function of plasma membrane 2ICHHA PURAK
The presentation consists of 72 slides,describes following heads
DEFINITION : STRUCTURE OF PLASMA MEMBRANE
COMPONENTS OF PLASMA MEMBRANE ( (BIOCHEMICAL PROPERTIES)
LIPID BILAYER
PROTEINS
CARBOHYDRATES
CHOLESTEROL
MODELS EXPLAINING STRUCTURE OF BIO MEMBRANE
FLUID MOSAIC MODEL
MOBILITY OF MEMBRANE
GLYCOCALYX : GLYCOPROTEINS AND GLYCOLIPIDS
TRANSPORT OF IONS AND MOLECULES ACROSS PLASMA MEMBRANE
FUNCTIONS OF PLASMA MEMBRANE
DIVERSITY OF CELL MEMBRANES
SITE OF ATPASE ION CARRIER CHANNELS AND PUMPS-RECEPTORS
The power point presentation includes 63 slides covering Nuclear Structure of Green Algae, Cell Cycle and process of Cell division, Mitosis and Meiosis, Chromosome Types recorded in green algae, Karyotypes : Ideograms, Chromosome numbers : Basic chromosome number, Polyploidy and Aneuploidy and Resistance or Susceptibility of chromosomes towards chemicals
This power point presentation consists of 64 slides including information about plant and other type of cell wall. Chemical composition, structure, function and properties of cell wall have been explained. Ultra structure of plant cell wall has also been high lighted. Algal,Fungal,Bacterial and Archaeal cell walls have also been explained.
Cell as basic unit of life ppt 88 slidesICHHA PURAK
This Power point presentation describes Cell as basic unit of life. The slides provide information about Discovery of cell,cell theory,number,size,shape and cell types .Differentiates prokaryotic and eukaryotic cell types and point out major differences in plant and animal cell and also about structure and function of cell organelles
Regulation of gene expression in prokaryotes finalICHHA PURAK
The power point presentation explains about regulation of gene expression in prokaryotes by means of Inducible and repressible operons with the help of Lactose(lac) operon and Tryptophan (trp)
Structure and function of Messenger RNA (mRNA )ICHHA PURAK
This presentation of 42 slides delivers information about structure,function synthesis , life span of both prokaryotic and eukaryotic messenger RNA also about role in protein sorting and targetting
The power point presentation consists of 36 slides explaining about history, principle, different steps involved and applications of DNA fingerprinting. Recent Developments and the Future prospects of DNA profiling have also been mentioned
Southern Blotting (SB) 4 jan 2015 finalICHHA PURAK
The power Point presentation contains 38 slides explaining about different steps involved in Southern Blotting such as DNA Isolation, Restriction digestion, Separation of DNA fragments by gel electrophoresis, denaturation of Double stranded DNA , transfer of fragments from gel to membrane ( blotting) , hybridization and detection by autoradiography. Applications of Southern blotting have also been discussed
Agrobacterium mediated gene transfer in plants.ICHHA PURAK
This power point presentation consist of 41 slides. Attempts have been made to illustrate how Agrobacterium behaves us natural genetic engineer. How it can infect a plant through wound and a part of DNA present on Ti plasmid is Tranferred and causes disease as crown gall in the infected plant. In second part of the presentation attempts have been made to describe how Agrobacterium can be utilized for iinsertion of desired gene into the plant,what manipulation are to be made with Agrobacterium.How infection and transfer of desired gene can be made possible.What is the role of plant tissue culture etc.
This power point presentation is designed to explain deviation of Mendelian dihybrid ratio due to interaction of genes which may be of following types
1.Two gene pairs affecting same character – 9:3:3:1
2.Epistasis, one gene hides effect of other
a) Recessive Epistasis - 9:3:4
b) Dominant epistasis - 12:3:1
3.Complementary genes - 9:7 ( 2 genes responsible for production of a particular phenotype )
4. Duplicate genes – 15:1 ( same effect given by either of two genes )
5. Polymeric gene action - 9:6:1
6. Inhibitory gene action - 13 : 3
Each interaction is typical in itself and ratios obtained are different
This Power Point Presentation is designed to explain Mendel's experiment on hybridization and dihybrid cross which considers inheritance of two traits at a time and to know whether they are inherited independently or are influenced by each other and also about Law of Independent assortment
DevOps and Testing slides at DASA ConnectKari Kakkonen
My and Rik Marselis slides at 30.5.2024 DASA Connect conference. We discuss about what is testing, then what is agile testing and finally what is Testing in DevOps. Finally we had lovely workshop with the participants trying to find out different ways to think about quality and testing in different parts of the DevOps infinity loop.
UiPath Test Automation using UiPath Test Suite series, part 3DianaGray10
Welcome to UiPath Test Automation using UiPath Test Suite series part 3. In this session, we will cover desktop automation along with UI automation.
Topics covered:
UI automation Introduction,
UI automation Sample
Desktop automation flow
Pradeep Chinnala, Senior Consultant Automation Developer @WonderBotz and UiPath MVP
Deepak Rai, Automation Practice Lead, Boundaryless Group and UiPath MVP
Slack (or Teams) Automation for Bonterra Impact Management (fka Social Soluti...Jeffrey Haguewood
Sidekick Solutions uses Bonterra Impact Management (fka Social Solutions Apricot) and automation solutions to integrate data for business workflows.
We believe integration and automation are essential to user experience and the promise of efficient work through technology. Automation is the critical ingredient to realizing that full vision. We develop integration products and services for Bonterra Case Management software to support the deployment of automations for a variety of use cases.
This video focuses on the notifications, alerts, and approval requests using Slack for Bonterra Impact Management. The solutions covered in this webinar can also be deployed for Microsoft Teams.
Interested in deploying notification automations for Bonterra Impact Management? Contact us at sales@sidekicksolutionsllc.com to discuss next steps.
Accelerate your Kubernetes clusters with Varnish CachingThijs Feryn
A presentation about the usage and availability of Varnish on Kubernetes. This talk explores the capabilities of Varnish caching and shows how to use the Varnish Helm chart to deploy it to Kubernetes.
This presentation was delivered at K8SUG Singapore. See https://feryn.eu/presentations/accelerate-your-kubernetes-clusters-with-varnish-caching-k8sug-singapore-28-2024 for more details.
Connector Corner: Automate dynamic content and events by pushing a buttonDianaGray10
Here is something new! In our next Connector Corner webinar, we will demonstrate how you can use a single workflow to:
Create a campaign using Mailchimp with merge tags/fields
Send an interactive Slack channel message (using buttons)
Have the message received by managers and peers along with a test email for review
But there’s more:
In a second workflow supporting the same use case, you’ll see:
Your campaign sent to target colleagues for approval
If the “Approve” button is clicked, a Jira/Zendesk ticket is created for the marketing design team
But—if the “Reject” button is pushed, colleagues will be alerted via Slack message
Join us to learn more about this new, human-in-the-loop capability, brought to you by Integration Service connectors.
And...
Speakers:
Akshay Agnihotri, Product Manager
Charlie Greenberg, Host
Builder.ai Founder Sachin Dev Duggal's Strategic Approach to Create an Innova...Ramesh Iyer
In today's fast-changing business world, Companies that adapt and embrace new ideas often need help to keep up with the competition. However, fostering a culture of innovation takes much work. It takes vision, leadership and willingness to take risks in the right proportion. Sachin Dev Duggal, co-founder of Builder.ai, has perfected the art of this balance, creating a company culture where creativity and growth are nurtured at each stage.
Software Delivery At the Speed of AI: Inflectra Invests In AI-Powered QualityInflectra
In this insightful webinar, Inflectra explores how artificial intelligence (AI) is transforming software development and testing. Discover how AI-powered tools are revolutionizing every stage of the software development lifecycle (SDLC), from design and prototyping to testing, deployment, and monitoring.
Learn about:
• The Future of Testing: How AI is shifting testing towards verification, analysis, and higher-level skills, while reducing repetitive tasks.
• Test Automation: How AI-powered test case generation, optimization, and self-healing tests are making testing more efficient and effective.
• Visual Testing: Explore the emerging capabilities of AI in visual testing and how it's set to revolutionize UI verification.
• Inflectra's AI Solutions: See demonstrations of Inflectra's cutting-edge AI tools like the ChatGPT plugin and Azure Open AI platform, designed to streamline your testing process.
Whether you're a developer, tester, or QA professional, this webinar will give you valuable insights into how AI is shaping the future of software delivery.
Epistemic Interaction - tuning interfaces to provide information for AI supportAlan Dix
Paper presented at SYNERGY workshop at AVI 2024, Genoa, Italy. 3rd June 2024
https://alandix.com/academic/papers/synergy2024-epistemic/
As machine learning integrates deeper into human-computer interactions, the concept of epistemic interaction emerges, aiming to refine these interactions to enhance system adaptability. This approach encourages minor, intentional adjustments in user behaviour to enrich the data available for system learning. This paper introduces epistemic interaction within the context of human-system communication, illustrating how deliberate interaction design can improve system understanding and adaptation. Through concrete examples, we demonstrate the potential of epistemic interaction to significantly advance human-computer interaction by leveraging intuitive human communication strategies to inform system design and functionality, offering a novel pathway for enriching user-system engagements.
State of ICS and IoT Cyber Threat Landscape Report 2024 previewPrayukth K V
The IoT and OT threat landscape report has been prepared by the Threat Research Team at Sectrio using data from Sectrio, cyber threat intelligence farming facilities spread across over 85 cities around the world. In addition, Sectrio also runs AI-based advanced threat and payload engagement facilities that serve as sinks to attract and engage sophisticated threat actors, and newer malware including new variants and latent threats that are at an earlier stage of development.
The latest edition of the OT/ICS and IoT security Threat Landscape Report 2024 also covers:
State of global ICS asset and network exposure
Sectoral targets and attacks as well as the cost of ransom
Global APT activity, AI usage, actor and tactic profiles, and implications
Rise in volumes of AI-powered cyberattacks
Major cyber events in 2024
Malware and malicious payload trends
Cyberattack types and targets
Vulnerability exploit attempts on CVEs
Attacks on counties – USA
Expansion of bot farms – how, where, and why
In-depth analysis of the cyber threat landscape across North America, South America, Europe, APAC, and the Middle East
Why are attacks on smart factories rising?
Cyber risk predictions
Axis of attacks – Europe
Systemic attacks in the Middle East
Download the full report from here:
https://sectrio.com/resources/ot-threat-landscape-reports/sectrio-releases-ot-ics-and-iot-security-threat-landscape-report-2024/
Essentials of Automations: Optimizing FME Workflows with ParametersSafe Software
Are you looking to streamline your workflows and boost your projects’ efficiency? Do you find yourself searching for ways to add flexibility and control over your FME workflows? If so, you’re in the right place.
Join us for an insightful dive into the world of FME parameters, a critical element in optimizing workflow efficiency. This webinar marks the beginning of our three-part “Essentials of Automation” series. This first webinar is designed to equip you with the knowledge and skills to utilize parameters effectively: enhancing the flexibility, maintainability, and user control of your FME projects.
Here’s what you’ll gain:
- Essentials of FME Parameters: Understand the pivotal role of parameters, including Reader/Writer, Transformer, User, and FME Flow categories. Discover how they are the key to unlocking automation and optimization within your workflows.
- Practical Applications in FME Form: Delve into key user parameter types including choice, connections, and file URLs. Allow users to control how a workflow runs, making your workflows more reusable. Learn to import values and deliver the best user experience for your workflows while enhancing accuracy.
- Optimization Strategies in FME Flow: Explore the creation and strategic deployment of parameters in FME Flow, including the use of deployment and geometry parameters, to maximize workflow efficiency.
- Pro Tips for Success: Gain insights on parameterizing connections and leveraging new features like Conditional Visibility for clarity and simplicity.
We’ll wrap up with a glimpse into future webinars, followed by a Q&A session to address your specific questions surrounding this topic.
Don’t miss this opportunity to elevate your FME expertise and drive your projects to new heights of efficiency.
Encryption in Microsoft 365 - ExpertsLive Netherlands 2024Albert Hoitingh
In this session I delve into the encryption technology used in Microsoft 365 and Microsoft Purview. Including the concepts of Customer Key and Double Key Encryption.
LF Energy Webinar: Electrical Grid Modelling and Simulation Through PowSyBl -...DanBrown980551
Do you want to learn how to model and simulate an electrical network from scratch in under an hour?
Then welcome to this PowSyBl workshop, hosted by Rte, the French Transmission System Operator (TSO)!
During the webinar, you will discover the PowSyBl ecosystem as well as handle and study an electrical network through an interactive Python notebook.
PowSyBl is an open source project hosted by LF Energy, which offers a comprehensive set of features for electrical grid modelling and simulation. Among other advanced features, PowSyBl provides:
- A fully editable and extendable library for grid component modelling;
- Visualization tools to display your network;
- Grid simulation tools, such as power flows, security analyses (with or without remedial actions) and sensitivity analyses;
The framework is mostly written in Java, with a Python binding so that Python developers can access PowSyBl functionalities as well.
What you will learn during the webinar:
- For beginners: discover PowSyBl's functionalities through a quick general presentation and the notebook, without needing any expert coding skills;
- For advanced developers: master the skills to efficiently apply PowSyBl functionalities to your real-world scenarios.
GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...
Dna replication part i
1. DNA REPLICATION PART-I
By
Dr. Ichha PuraK
University Professor
Department of Botany
Ranchi Women’s College,Ranchi
www.dripurak.com
6/15/2013DNA REPLICATION Part-I1
2. DNA REPLICATION
INTRODUCTION
IMPORTANCE OF REPLICATION
THE REPLICATION FACTORY
•MODE OF REPLICATION : SEMI CONSERVATIVE
•EXPERIMENTAL EVIDENCE
•PHASE OF REPLICATION
•PLACE OF REPLICATION
•DIRECTION OF REPLICATION
•INITIATION OF REPLICATION : PROKARYOTES
•EUKARYOTIC INITIATION OF REPLICATION
•PROTEINS AND ENZYMES INVOLVED IN REPLICATION
•REPLICATION FORK
6/15/2013DNA REPLICATION Part-I2
3. DNA replication is a fundamental process by which the parent DNA
duplex copies itself and become duplicated and produce two daughter
DNA duplexes .
Both strands of DNA ladder separate and act as template, onto which
new daughter strands are assembled, for which complementary
deoxyribonucleotides are taken from pool of deoxyribonucleotides.
The two DNA duplexes that emerge from this process receive only one
side of original DNA and other side newly synthesized.
6/15/2013DNA REPLICATION Part-I3
4. IMPORTANCE OF REPLICATION
It is one of the most vital processes. It provides means by which
genetic instructions can be transmitted from one (parent ) cell to its
two daughter cells or from one individual to its offsprings because
during Replication Parent DNA duplex is able to make its two
identical copies or Replica and It is now well known that DNA is the
Genetic Material,able to transmit information over generations.
6/15/2013DNA REPLICATION Part-I4
5. 6/15/2013DNA REPLICATION Part-I5
DNA Template
New DNA
PARENTAL DNA
Semi-conservative
Model:
Watson and Crick
predicted : the two
strands of the
parental molecule
separate, and each
functions as a
template for synthesis
of a new
complementary
strand.
8. THE REPLICATION FACTORY
Replication proteins are clustered together in particular locations in the
cell and may therefore be regarded as Replication Factory that
manufactures DNA copies.
The DNA to be copied is fed through the factory, much as a reel of film is
fed through a movie projector. The incoming DNA double helix is split
into two single strands and each original strand becomes half of a new
double helix. Because each resulting DNA double helix retains one
strand of the original DNA. DNA replication is said to be semi-
conservative
6/15/2013DNA REPLICATION Part-I8
10. MODE OF REPLICATION :
Three possibilities have been suggested as mode for replication :
•Conservative Of the two duplexes produced after replication one is
entirely parental and other entirely new
•Semi-conservative Both the two duplexes formed after replication
contain one parental strand and one newly synthesized strand. Parent
DNA double helix is not conserved as entity, But one parental strand is
conserved in both daughter double helices in each generation and it
continues for many generations.
•Dispersive Both strands of parental molecule break at random, after
replication the parental and daughter pieces are joined randomly.
6/15/2013DNA REPLICATION Part-I10
12. Of the various ideas proposed regarding mode of replication viz.
conservative, semi-conservative and dispersive, the semi-
conservative mode is highly accepted , which indicates that one
half of the parent duplex is transmitted to each daughter duplex. It
has been theoretically predicted by Watson and Crick ( 1953) on
the basis of double helical nature and complementary sequence of
bases on two strands of DNA.
6/15/2013DNA REPLICATION Part-I12
Semi conservative mode of replication has been experimentally
proved by Maselson and Stahl (1958) using 15N in the nutrient
medium for culturing E.coli and monitoring the density of DNA after
each replication
13. EXPERIMENTAL EVIDENCE
Steps in the Experiment
1.E. coli cells were grown in culture medium having NH4Cl (with15N)
as Nitrogen source for 14 generations, so that all DNA bases
become labeled. This heavier ( High density) DNA settles
differently after centrifugation than the lighter (Low Density ) DNA
having 14 N.
2. E.coli cells were then removed ,washed and transferred to
culture medium having NH4Cl ( with 14 N) as Nitrogen source.
3. Some cells of E. coli were removed after every 30 minutes and
DNA was extracted and examined for density by centrifugation
with Cesium Chloride solution followed by sedimentation. ( E coli
takes 30 minutes for one division)
6/15/2013DNA REPLICATION Part-I13
14. The results were observed :
4. After first generation only one band was observed by ultraviolet
absorption(260 nm) and it showed density intermediate between
heavier ( DNA 15 N) and lighter (DNA 14 N ) DNA s.
5. After two generations two bands were seen, one comparable to
Intermediate (Hybrid) DNA density and other of Normal ( DNA 14 N )
density.
6. In all subsequent generations two bands appeared, but intensity of
Hybrid density band gradually decreased and band of lighter DNA
gradually increased as expected by Semiconservative mode of
replication.
6/15/2013DNA REPLICATION Part-I14
20. PHASE OF REPLICATION
Takes place during ‘S’ (Synthetic) phase of the preparatory stage of
cell cycle which commences after G 1 and is followed by G 2. The
preparatory stage is also known as Resting stage as cell is supposed to
be not active in division. It is also known as Interphase as it is the
period in between two cell divisions. During this period cell is
metabolically active.
6/15/2013DNA REPLICATION Part-I20
21. Eukaryotic Replication having many origins
PLACE OF REPLICATION
It starts at origins of replication (Ori), appears as bubble under
electron microscope, ultimately extend in the form of ‘Y’
shaped replication fork.
6/15/2013DNA REPLICATION Part-I21
25. 6/15/2013DNA REPLICATION Part-I25
DIRECTION OF REPLICATION
Replication takes place in bi-directional way, proceeds on both
sides of origin of replication ( Ori), both in pro as well as
eukaryotes. DNA synthesis takes place in 5’--------> 3’ direction and
the template is read in 3’ --------> 5’ direction so two newly
synthesized stretches of nucleotide chains must grow in opposite
direction . On one direction new strand grows towards fork and on
other strand away from the fork.
26. 6/15/2013DNA REPLICATION Part-I26
Thetalike configuration
assumed by
replicating,circular,no-end
double helical DNA
molecule of Escherichia
coli. Arrows indicate the two
replication forks. These
have progressed
bidirectionally from a single
replication bubble
In Bacteria, as DNA is circular and there is single (Ori), bi-directional
replication gives a shape.
27. Pattern of replication
of long DNA
molecule with more
than one origin of
replication.
Replication proceeds
out bidirectionally
from each origin
6/15/2013DNA REPLICATION Part-I27
29. Origin of replication in E.coli
Replication initiates at a Unique site on
the E.coli chromosome ,designated as
ori.
First event is the binding of an initiator
protein to ori DNA , which leads to
partial unwinding of the DNA double
helix giving two templates
DNA continues to unwind by the
action of Helicase and single
stranded DNA binding proteins and
RNA primers synthesized by Primase
The two replication forks formed at
the origin then move in opposite
directions along the circular DNA
molecule
6/15/2013DNA REPLICATION Part-I29
30. INITIATION OF REPLICATION : FACTORS INVOLVED
Prokaryotes : Eubacterial cell : E.coli
Initiation begins at A -T rich sequences at Ori C in E.coli. The main
components of the replication complex formation are ORC
(Origin Recognition Complex), factors Dna A, Dna B, Dna C, HU
and enzyme helicase. Dna A binding site consists of 9 bp repeats of
5’TGTGAATAA 3’, it binds to the Ori C , sets the platform and promotes
double helical opening, it also loads Dna B .
6/15/2013DNA REPLICATION Part-I30
31. Binding of Dna A protein appears to be the key event ,it appears as
ellipsoidal mass (Dna A-Ori C ) under electron microscope. Dna B
has 5’ 3’ helicase activity and is also activator of primase Dna C
complex. HU is another double stranded binding protein.
As ORC binds DNA with the help of different protein factors, the
double helical structure opens in the form of small bubble by the
enzyme helicase. Once double helical structure is opened, it is
stabilized by single stranded DNA binding proteins.
6/15/2013DNA REPLICATION Part-I31
32. EUKARYOTIC INITIATION OF REPLICATION : FACTORS
INVOLVED
Eukaryotic DNA is complexed with proteins, is assembled as
chromosomes. Eukaryotic DNA is many times larger than
prokaryotic DNA and therefore have multiple origin of
replication (ori) sites. The average human chromosome contains
150x106 nucleotide pairs, which are copied at about 50 bp per
sec speed. But due to presence of multiple origin of replication,
whole genome is replicated in 1 hour. In order to initiate
replication at these multiple sites a pre replicative complex is
formed having the following components :
6/15/2013DNA REPLICATION Part-I32
33. ORC ( Origin Recognition Complex ) ,these remain bound to
DNA through out the Initiation process and is a six subunit
complex. It has affinity for single stranded DNA. Other factors
help ORC in identifying the ori sites. Its binding is coupled with
ATP hydrolysis.
CdC6 protein associates with ORC and help MCM proteins to
associate with chromatin.
Cdt 1 protein is identified as key factor in Pre-Rc assembly, so
mutations in Cdt 1 (In vitro studies ) results in a block to DNA
replication.
6/15/2013DNA REPLICATION Part-I33
36. MCM (Mini chromosome Maintenance ) proteins - DNA is coated
with these proteins with the help of CdC6 and Cdt1. Once
replication begins in S phase,Cdt1 and CdC6 leave the ORCs and
MCM proteins remain in front of Replication fork on both sides
and all these help in stabilizing replication fork and its extension
having single stranded DNA.
DNA synthesis begins with the activity of DNA helicase which
causes melting of hydrogen bonds between base pairs ( A- T and
G-C) . As a result two single stranded structures with their
exposed nucleotides are produced.
6/15/2013DNA REPLICATION Part-I36
37. These single strands have a tendency to wound again (make
base pairs) and to avoid this single stranded DNA binding
proteins play important role. They also protect the single
stranded structures from nucleases. After this DNA polymerase
comes into action. It selects the complementary nucleotide
from a mixture of dNTPs ( dATP,dCTP, dGTP,dTTP) and add to
the template strand and also establish phosphodi-ester bonds
between successive nucleotides.
6/15/2013DNA REPLICATION Part-I37
38. PROTEINS AND ENZYMES INVOLVED IN
REPLICATION
Many enzymes and proteins are involved in the process of DNA
Replication to unwind double helix,replication fork stabilization
and synthesizing new DNA strand reading the template.viz.
Helicase, SSB Protein, Primase, The sliding Clamp, DNA
Polymerase, Rnase H and DNA Ligase. Each enzymes has a
specific role.
DNA replication requires a variety of proteins. Each protein
performs a specific function in the production of the new DNA
strands.
Helicase, made of six proteins arranged in a ring shape, unwinds
the DNA double helix into two individual strands.
6/15/2013DNA REPLICATION Part-I38
39. Single-strand binding proteins, or SSBs, are tetramers that coat the
single-stranded DNA. This prevents the DNA strands from
reannealing to form double-stranded DNA. Primase is an RNA
polymerase that synthesizes the short RNA primers needed to start
the strand replication process. DNA polymerase is a hand-shaped
enzyme that strings nucleotides together to form a DNA strand. The
sliding clamp is an accessory protein that helps hold the DNA
polymerase onto the DNA strand during replication. RNAse H
removes the RNA primers that previously began the DNA strand
synthesis. DNA ligase links short stretches of DNA together to
create one long continuous DNA strand.
6/15/2013DNA REPLICATION Part-I39
42. DNA Gyrase ( Type II Topoisomerase). Helps unwinding by DNA
helicase. Reduces the tension caused by super coil formation during
unwinding. For it single nick is created by breaking the phosphodiester
bond on one of the strand, which helps to release tension .
Topoisomerases have both nuclease (strand cutting) and ligase (strand
resealing) activities.
DNA helicase Helps in dissolving ‘H’ bonds between base pairs and
result in separating the two strands near origin of replication, which
gradually extends. Helicase as it requires energy to open the duplex is
associated with hydrolysis of ATP.
Singe stranded DNA binding Proteins Maintain the stability of
replication fork by binding the separated strands on both sides and
keeping them apart to avoid rewinding.These proteins also protect the
exposed nucleotides on the separated strands against nucleases.
6/15/2013DNA REPLICATION Part-I42
43. DNA Polymerase Proceeds along the single stranded
templates , recruit complementary dNTPs, form Hydrogen
bonds with their appropriate complementary base present on
the template and catalyze phosphodiester bond with previous
nucleotide of the same strand.In prokaryotes DP III is
responsible for synthesis of new DNA strands .DP I is involved
in replacing deoxyribonucleotides after removal of RNA primers
on the lagging strand.
The sliding clamp is an accessory protein that helps hold the
DNA polymerase onto the DNA strand during replication.
RNA Primase Is actually part of aggregates of proteins called
primosomes. This enzyme attaches a small RNA primer to the
single stranded DNA onto which DP III can add
deoxyribonucleotides.
6/15/2013DNA REPLICATION Part-I43
44. RNase This enzyme dismantles the RNA primers
present at the 5’ end of each Okazaki fragment on
lagging strand and also single RNA primer present on
the leading strand at the 5’ end.
DNA ligase Can catalyse the formation of
phosphodiester bond between 3’OH and 5’
phosphate groups of two DNA fragments on lagging
strand after removal of RNA primers. They seal the
gaps between two such DNA pieces.
6/15/2013DNA REPLICATION Part-I44
45. REPLICATION FORK
The point where the DNA is separated into single strands, and
where new DNA will be synthesized, is known as the replication
fork.
For replication to take place the two strands of DNA double
helix at weak spots ( Where more A------- T base pairing is present )
separate by dissolving Hydrogen bond. The separated strands
appear as bubble under Electron Microscope. The two halves of
this bubble look as Y shaped Replication Fork with Neck and Mouth.
In prokaryotes there is single origin (Ori) , where as in Eukaryotes
several Ori are present.
6/15/2013DNA REPLICATION Part-I45
47. DNA replication
“It has not escaped our
notice that the specific
pairing we have postulated
immediately suggests a
possible copying mechanism
for the genetic material.”
James Watson
Francis Crick
1953