The document discusses regulation of the cell cycle through cyclins, CDKs, and ubiquitin ligases. It covers the four phases of the cell cycle (G1, S, G2, M), regulation of DNA replication and mitosis, checkpoints that ensure quality control, and mechanisms that propel quiescent cells into the cell cycle in response to mitogens. The precise ordering and timing of cell cycle events is controlled by the periodic synthesis and degradation of cyclins and other regulatory proteins.
The document summarizes key aspects of the cell cycle and its control mechanisms. It describes the main phases of the eukaryotic cell cycle - G1, S, G2, and M phase. It explains that cyclins and cyclin-dependent kinases (CDKs) control progression between phases by promoting specific events like DNA replication and mitosis. CDK activity is regulated by binding with cyclins and proteolytic degradation of cyclins by the anaphase promoting complex. Checkpoints in the cell cycle arrest progression under negative intracellular signals to ensure DNA replication and chromosome separation are properly completed.
The cell cycle is regulated by cyclin-dependent kinases (Cdks) whose activity oscillates throughout the cycle. Cdks form complexes with cyclins, which activate the Cdks and determine which phase of the cycle they control. The cyclin-Cdk complexes phosphorylate target proteins to promote replication and mitosis. Progression through the cell cycle is also controlled by ubiquitin ligases and phosphorylation/dephosphorylation events. The cycle operates through a series of switches that trigger irreversible events, keeping it tightly regulated and coordinated.
The cell cycle consists of interphase and the mitotic phase. Interphase includes the G1, S, and G2 phases where the cell grows and prepares for division. The mitotic phase includes mitosis where the cell divides into two daughter cells. Cyclin-dependent kinases (CDKs) and cyclins control progression through the cell cycle by phosphorylating proteins. CDK-cyclin complexes activate at different phases, such as cyclin D-CDK4 in G1 and cyclin B-CDK1 in mitosis. Checkpoints in G1/S and G2/M ensure DNA is intact before the cell divides.
The cell cycle involves an orderly sequence of events where a cell duplicates its contents and divides into two daughter cells. It consists of interphase, where the cell grows and DNA replicates, and M phase where the cell divides. Key phases of interphase include G1, S, and G2 phases separated by gap phases. The cell cycle is tightly regulated by cyclins and CDKs which form complexes to drive the cell through checkpoints between phases. DNA replication only occurs once per cycle through control of initiation factors. Sister chromatids are held together by cohesin until anaphase.
The document summarizes the cell cycle and its regulation. It discusses the main phases of the cell cycle including interphase (G1, S, G2 phases) and the M phase. It also describes key cell cycle checkpoints and the proteins involved in regulating progression through the cycle, such as cyclins, CDKs, and CDK inhibitors. Precise control of the cell cycle is essential as any errors could lead to cancer.
The cell cycle is regulated by cyclins and cyclin-dependent kinases (Cdks). Cyclins activate Cdks to phosphorylate proteins and trigger transitions between phases such as G1 to S and G2 to M. Checkpoints ensure completion of earlier steps before progression. The levels of cyclins and activity of Cdks are regulated by other proteins in response to internal signals, like DNA replication status, and external signals, like growth factors, to control the cell cycle.
Cell cycle and its regulation . topic from essential of genetics.pptxMuhammadMusharaf17
Mutations in key molecules that regulate the cell cycle can disrupt the orderly progression of the cell cycle and allow uncontrolled cell division, a hallmark of cancer.
For example:
- Mutations that activate oncogenes encoding proteins involved in cell cycle progression, like cyclins and CDKs, could drive continuous cycling and proliferation.
- Mutations that inactivate tumor suppressor genes encoding proteins that normally inhibit cell cycle progression or induce apoptosis in damaged cells could prevent checkpoints from halting the cell cycle under inappropriate conditions.
So in summary, mutations disrupting the normal function of cell cycle regulatory molecules have the potential to undermine cellular controls over division, thereby enabling unchecked growth and the development of cancer. Maintaining the fidelity of
This document summarizes key aspects of the cell cycle and its regulation. It describes the main phases of the eukaryotic cell cycle including interphase and mitosis. Checkpoints that ensure DNA replication fidelity like ATM/ATR pathways are discussed. Central regulators of the cell cycle like cyclins, CDKs, and CDK inhibitors are covered. The roles of Rb and p53 tumor suppressors are mentioned. The stages of mitosis and spindle assembly checkpoint are briefly outlined.
The document summarizes key aspects of the cell cycle and its control mechanisms. It describes the main phases of the eukaryotic cell cycle - G1, S, G2, and M phase. It explains that cyclins and cyclin-dependent kinases (CDKs) control progression between phases by promoting specific events like DNA replication and mitosis. CDK activity is regulated by binding with cyclins and proteolytic degradation of cyclins by the anaphase promoting complex. Checkpoints in the cell cycle arrest progression under negative intracellular signals to ensure DNA replication and chromosome separation are properly completed.
The cell cycle is regulated by cyclin-dependent kinases (Cdks) whose activity oscillates throughout the cycle. Cdks form complexes with cyclins, which activate the Cdks and determine which phase of the cycle they control. The cyclin-Cdk complexes phosphorylate target proteins to promote replication and mitosis. Progression through the cell cycle is also controlled by ubiquitin ligases and phosphorylation/dephosphorylation events. The cycle operates through a series of switches that trigger irreversible events, keeping it tightly regulated and coordinated.
The cell cycle consists of interphase and the mitotic phase. Interphase includes the G1, S, and G2 phases where the cell grows and prepares for division. The mitotic phase includes mitosis where the cell divides into two daughter cells. Cyclin-dependent kinases (CDKs) and cyclins control progression through the cell cycle by phosphorylating proteins. CDK-cyclin complexes activate at different phases, such as cyclin D-CDK4 in G1 and cyclin B-CDK1 in mitosis. Checkpoints in G1/S and G2/M ensure DNA is intact before the cell divides.
The cell cycle involves an orderly sequence of events where a cell duplicates its contents and divides into two daughter cells. It consists of interphase, where the cell grows and DNA replicates, and M phase where the cell divides. Key phases of interphase include G1, S, and G2 phases separated by gap phases. The cell cycle is tightly regulated by cyclins and CDKs which form complexes to drive the cell through checkpoints between phases. DNA replication only occurs once per cycle through control of initiation factors. Sister chromatids are held together by cohesin until anaphase.
The document summarizes the cell cycle and its regulation. It discusses the main phases of the cell cycle including interphase (G1, S, G2 phases) and the M phase. It also describes key cell cycle checkpoints and the proteins involved in regulating progression through the cycle, such as cyclins, CDKs, and CDK inhibitors. Precise control of the cell cycle is essential as any errors could lead to cancer.
The cell cycle is regulated by cyclins and cyclin-dependent kinases (Cdks). Cyclins activate Cdks to phosphorylate proteins and trigger transitions between phases such as G1 to S and G2 to M. Checkpoints ensure completion of earlier steps before progression. The levels of cyclins and activity of Cdks are regulated by other proteins in response to internal signals, like DNA replication status, and external signals, like growth factors, to control the cell cycle.
Cell cycle and its regulation . topic from essential of genetics.pptxMuhammadMusharaf17
Mutations in key molecules that regulate the cell cycle can disrupt the orderly progression of the cell cycle and allow uncontrolled cell division, a hallmark of cancer.
For example:
- Mutations that activate oncogenes encoding proteins involved in cell cycle progression, like cyclins and CDKs, could drive continuous cycling and proliferation.
- Mutations that inactivate tumor suppressor genes encoding proteins that normally inhibit cell cycle progression or induce apoptosis in damaged cells could prevent checkpoints from halting the cell cycle under inappropriate conditions.
So in summary, mutations disrupting the normal function of cell cycle regulatory molecules have the potential to undermine cellular controls over division, thereby enabling unchecked growth and the development of cancer. Maintaining the fidelity of
This document summarizes key aspects of the cell cycle and its regulation. It describes the main phases of the eukaryotic cell cycle including interphase and mitosis. Checkpoints that ensure DNA replication fidelity like ATM/ATR pathways are discussed. Central regulators of the cell cycle like cyclins, CDKs, and CDK inhibitors are covered. The roles of Rb and p53 tumor suppressors are mentioned. The stages of mitosis and spindle assembly checkpoint are briefly outlined.
The cell cycle involves an interphase of growth and DNA replication followed by mitosis, where the cell divides. The cell cycle is regulated by cyclins and cyclin-dependent kinases (CDKs) that drive progression between phases. CDK activity increases upon binding to cyclins and decreases when cyclins are degraded. Growth hormones like auxins and cytokinins promote cell cycle progression by increasing cyclin and CDK expression, while abscisic acid inhibits the cell cycle. Together, these regulatory mechanisms precisely control cell division.
Eukayotic_cell_cycle-diff_phases_mol_events
Different Phases and Molecular Events
-Control mechanisms: Role of
(A) Cyclins and cyclin-dependent kinases
(B) Retinoblastoma and E2F proteins
-Cytokinesis and cell plate formation
The document summarizes key aspects of the cell cycle and cell signaling. It describes the main phases of the cell cycle (G1, S, G2, M), checkpoints that ensure proper cell division, and cyclins and cyclin-dependent kinases that regulate transition between phases. It also covers meiosis, which produces gametes through one round of DNA replication followed by two cell divisions, and mitosis, the process of nuclear division that results in two identical daughter cells during regular cell growth and renewal.
1. The document discusses the cell cycle, which is divided into four phases, and the cell cycle control system which triggers progression through the phases.
2. The cell cycle control system depends on cyclin-dependent kinases (Cdks) whose activity is regulated by cyclical activation and inhibitory mechanisms.
3. The control system functions as a network of biochemical switches that drive DNA replication in S phase and chromosome segregation in mitosis.
The document summarizes the cell cycle and its checkpoints. It describes the different phases of the cell cycle including interphase consisting of G1, S, and G2 phases and the mitotic phase. Checkpoints ensure the cell cycle processes are accurately completed before progression including the G1, G2, and metaphase checkpoints. The cell cycle is regulated by cyclins, cyclin-dependent kinases, and cyclin-dependent kinase inhibitors that act as positive and negative regulators.
New Microsoft Office PowerPoint Presentation-1.pptxShounakKamat1
The cell cycle is a precisely programmed series of events that enables a cell to duplicate its contents and divide into two daughter cells. It consists of interphase (G1, S, G2 phases) and mitosis (M phase). Progression through the cell cycle is regulated by cyclins and cyclin-dependent kinases (CDKs). CDK activity is controlled by association with cyclins, CDK inhibitors, and phosphorylation. Checkpoint pathways like the G1/S, G2, and spindle assembly checkpoints ensure replication and division errors are corrected before progression. Deregulation of these checkpoint pathways can lead to genomic instability and carcinogenesis.
The document summarizes key aspects of the cell cycle. It discusses that the cell cycle is a series of events that a cell passes through from the time it is formed until it replicates. There are two main periods - interphase and mitosis. Interphase consists of G1, S, and G2 phases where the cell grows and duplicates its DNA. Mitosis is where the cell nucleus and cytoplasm divide. The cell cycle is tightly regulated by checkpoints and cyclins/CDKs to ensure DNA is properly replicated and divided between daughter cells. Dysregulation of cell cycle controls can lead to cancer if cells continue dividing uncontrollably.
The document discusses the cell cycle and its regulation. It can be summarized as follows:
1) The cell cycle consists of interphase (G1, S, G2 phases) and mitosis (M phase), where the cell grows and replicates its DNA before dividing.
2) Transition between phases is regulated by cyclins and cyclin-dependent kinases (CDKs), which promote progression.
3) There are checkpoints between phases to ensure DNA replication and cell division occur accurately before the cell cycle continues.
The document summarizes key aspects of cell cycle regulation in plants. It discusses the cell cycle phases of interphase (G1, S, G2) and mitosis. Key regulators of the plant cell cycle include cyclin-dependent kinases (CDKs) and cyclins. CDKs activate during specific cell cycle phases upon binding to cyclins. Plant hormones also influence the cell cycle through effects on CDKs, cyclins and other regulators. Precise control of the cell cycle is important for plant growth and development.
Cell cycle and regulation in eukaryotesBhanu Krishan
The document summarizes key aspects of the cell cycle and its regulation in human cells. It describes the main phases of the cell cycle - interphase (which includes G1, S, and G2 phases) and mitotic phase. It also discusses the roles of cyclins and cyclin-dependent kinases (CDKs) in controlling progression through the cell cycle. CDK-cyclin complexes form to phosphorylate target proteins and drive progression between phases. Different CDK-cyclin pairs function to regulate DNA replication and chromosome segregation during cell division.
The document provides information about the cell cycle and cell division. It discusses the key phases of the cell cycle (G1, S, G2, M), as well as important cell cycle checkpoints. It also describes the processes of mitosis and meiosis in detail, including the specific phases of each (prophase, metaphase, anaphase, telophase). Additionally, it discusses the roles and regulation of cyclins and CDKs in controlling the cell cycle. Finally, it notes some of the significance of cell division and potential errors that can occur.
The document provides an overview of the cell cycle, including its key phases (interphase consisting of G1, S, and G2 phases and the M phase), events that occur during each phase such as DNA replication in S phase, and control mechanisms. It discusses critical cell cycle regulators like cyclins and CDKs that form complexes to drive the cell cycle forward, as well as checkpoints that monitor cell growth and DNA integrity to ensure cells are ready to progress through the cycle. The cell cycle is tightly regulated by both intrinsic factors including cyclins and CDKs, and extrinsic factors like growth factors that influence division.
The cell cycle is the regulated process by which cells grow and divide to produce two daughter cells. It has two main phases: interphase and mitosis. Interphase consists of G1, S, and G2 phases where the cell grows and duplicates its DNA. Mitosis is when the cell divides. The cell cycle is regulated by cyclins, cyclin-dependent kinases (CDKs), and CDK inhibitors. Checkpoints ensure DNA quality and control cell cycle progression. Cell cycle dysregulation can lead to uncontrolled cell division and cancer.
Cell Cycle and Its Control Mechanism : Devendra KumarDevendra Kumar
The document provides an overview of the cell cycle and its control mechanisms. It discusses the different phases of the cell cycle including interphase (G1, S, G2 phases) and mitosis. It describes various checkpoints that monitor the cell cycle, including checkpoints at the G1/S transition and G2/M transition. Key regulators of the cell cycle include cyclins and cyclin-dependent kinases that promote phase transitions, as well as cyclin-dependent kinase inhibitors that inhibit transitions in response to errors or damage.
The cell cycle consists of four main phases - G1, S, G2, and M. In G1, cells grow and undergo protein synthesis in preparation for DNA replication. The S phase is when DNA replication occurs. In G2, the cell prepares for mitosis by producing necessary proteins. During mitosis (M phase), the nucleus and cell contents divide to form two daughter cells each with identical DNA. The progression through the cell cycle phases is regulated by cyclins and cyclin-dependent kinases (CDKs). Different cyclins activate specific CDKs to promote the transition between phases, with checkpoints ensuring errors are corrected before progression.
The document summarizes key aspects of cell cycle regulation. It discusses how experiments in the 1970s showed that the cytoplasm of mitotic cells contains factors that induce mitosis in non-mitotic cells, identifying maturation-promoting factor (MPF) as the key regulator. MPF consists of a catalytic subunit (Cdk) and a regulatory subunit (cyclin). Cyclin concentration varies throughout the cell cycle, activating Cdk at specific phases to drive progression. Precise phosphorylation of proteins by cyclin-Cdk complexes promotes cell cycle transitions through start and checkpoints.
The cell cycle is the ordered series of events that leads to cell division into two daughter cells. It consists of four main phases: G1, S, G2, and M. Checkpoints ensure each step is completed before progression. Cyclins activate CDKs at specific phases - G1 cyclins activate G1 CDKs which promote DNA replication by phosphorylating Rb and activating E2Fs. S-phase CDKs activate DNA replication origins. Mitotic CDKs promote mitotic events like spindle formation and chromosome condensation. Completion of mitosis involves chromosome segregation and cyclin degradation to inactivate CDKs and allow cell division.
Philippine Edukasyong Pantahanan at Pangkabuhayan (EPP) CurriculumMJDuyan
(𝐓𝐋𝐄 𝟏𝟎𝟎) (𝐋𝐞𝐬𝐬𝐨𝐧 𝟏)-𝐏𝐫𝐞𝐥𝐢𝐦𝐬
𝐃𝐢𝐬𝐜𝐮𝐬𝐬 𝐭𝐡𝐞 𝐄𝐏𝐏 𝐂𝐮𝐫𝐫𝐢𝐜𝐮𝐥𝐮𝐦 𝐢𝐧 𝐭𝐡𝐞 𝐏𝐡𝐢𝐥𝐢𝐩𝐩𝐢𝐧𝐞𝐬:
- Understand the goals and objectives of the Edukasyong Pantahanan at Pangkabuhayan (EPP) curriculum, recognizing its importance in fostering practical life skills and values among students. Students will also be able to identify the key components and subjects covered, such as agriculture, home economics, industrial arts, and information and communication technology.
𝐄𝐱𝐩𝐥𝐚𝐢𝐧 𝐭𝐡𝐞 𝐍𝐚𝐭𝐮𝐫𝐞 𝐚𝐧𝐝 𝐒𝐜𝐨𝐩𝐞 𝐨𝐟 𝐚𝐧 𝐄𝐧𝐭𝐫𝐞𝐩𝐫𝐞𝐧𝐞𝐮𝐫:
-Define entrepreneurship, distinguishing it from general business activities by emphasizing its focus on innovation, risk-taking, and value creation. Students will describe the characteristics and traits of successful entrepreneurs, including their roles and responsibilities, and discuss the broader economic and social impacts of entrepreneurial activities on both local and global scales.
The cell cycle involves an interphase of growth and DNA replication followed by mitosis, where the cell divides. The cell cycle is regulated by cyclins and cyclin-dependent kinases (CDKs) that drive progression between phases. CDK activity increases upon binding to cyclins and decreases when cyclins are degraded. Growth hormones like auxins and cytokinins promote cell cycle progression by increasing cyclin and CDK expression, while abscisic acid inhibits the cell cycle. Together, these regulatory mechanisms precisely control cell division.
Eukayotic_cell_cycle-diff_phases_mol_events
Different Phases and Molecular Events
-Control mechanisms: Role of
(A) Cyclins and cyclin-dependent kinases
(B) Retinoblastoma and E2F proteins
-Cytokinesis and cell plate formation
The document summarizes key aspects of the cell cycle and cell signaling. It describes the main phases of the cell cycle (G1, S, G2, M), checkpoints that ensure proper cell division, and cyclins and cyclin-dependent kinases that regulate transition between phases. It also covers meiosis, which produces gametes through one round of DNA replication followed by two cell divisions, and mitosis, the process of nuclear division that results in two identical daughter cells during regular cell growth and renewal.
1. The document discusses the cell cycle, which is divided into four phases, and the cell cycle control system which triggers progression through the phases.
2. The cell cycle control system depends on cyclin-dependent kinases (Cdks) whose activity is regulated by cyclical activation and inhibitory mechanisms.
3. The control system functions as a network of biochemical switches that drive DNA replication in S phase and chromosome segregation in mitosis.
The document summarizes the cell cycle and its checkpoints. It describes the different phases of the cell cycle including interphase consisting of G1, S, and G2 phases and the mitotic phase. Checkpoints ensure the cell cycle processes are accurately completed before progression including the G1, G2, and metaphase checkpoints. The cell cycle is regulated by cyclins, cyclin-dependent kinases, and cyclin-dependent kinase inhibitors that act as positive and negative regulators.
New Microsoft Office PowerPoint Presentation-1.pptxShounakKamat1
The cell cycle is a precisely programmed series of events that enables a cell to duplicate its contents and divide into two daughter cells. It consists of interphase (G1, S, G2 phases) and mitosis (M phase). Progression through the cell cycle is regulated by cyclins and cyclin-dependent kinases (CDKs). CDK activity is controlled by association with cyclins, CDK inhibitors, and phosphorylation. Checkpoint pathways like the G1/S, G2, and spindle assembly checkpoints ensure replication and division errors are corrected before progression. Deregulation of these checkpoint pathways can lead to genomic instability and carcinogenesis.
The document summarizes key aspects of the cell cycle. It discusses that the cell cycle is a series of events that a cell passes through from the time it is formed until it replicates. There are two main periods - interphase and mitosis. Interphase consists of G1, S, and G2 phases where the cell grows and duplicates its DNA. Mitosis is where the cell nucleus and cytoplasm divide. The cell cycle is tightly regulated by checkpoints and cyclins/CDKs to ensure DNA is properly replicated and divided between daughter cells. Dysregulation of cell cycle controls can lead to cancer if cells continue dividing uncontrollably.
The document discusses the cell cycle and its regulation. It can be summarized as follows:
1) The cell cycle consists of interphase (G1, S, G2 phases) and mitosis (M phase), where the cell grows and replicates its DNA before dividing.
2) Transition between phases is regulated by cyclins and cyclin-dependent kinases (CDKs), which promote progression.
3) There are checkpoints between phases to ensure DNA replication and cell division occur accurately before the cell cycle continues.
The document summarizes key aspects of cell cycle regulation in plants. It discusses the cell cycle phases of interphase (G1, S, G2) and mitosis. Key regulators of the plant cell cycle include cyclin-dependent kinases (CDKs) and cyclins. CDKs activate during specific cell cycle phases upon binding to cyclins. Plant hormones also influence the cell cycle through effects on CDKs, cyclins and other regulators. Precise control of the cell cycle is important for plant growth and development.
Cell cycle and regulation in eukaryotesBhanu Krishan
The document summarizes key aspects of the cell cycle and its regulation in human cells. It describes the main phases of the cell cycle - interphase (which includes G1, S, and G2 phases) and mitotic phase. It also discusses the roles of cyclins and cyclin-dependent kinases (CDKs) in controlling progression through the cell cycle. CDK-cyclin complexes form to phosphorylate target proteins and drive progression between phases. Different CDK-cyclin pairs function to regulate DNA replication and chromosome segregation during cell division.
The document provides information about the cell cycle and cell division. It discusses the key phases of the cell cycle (G1, S, G2, M), as well as important cell cycle checkpoints. It also describes the processes of mitosis and meiosis in detail, including the specific phases of each (prophase, metaphase, anaphase, telophase). Additionally, it discusses the roles and regulation of cyclins and CDKs in controlling the cell cycle. Finally, it notes some of the significance of cell division and potential errors that can occur.
The document provides an overview of the cell cycle, including its key phases (interphase consisting of G1, S, and G2 phases and the M phase), events that occur during each phase such as DNA replication in S phase, and control mechanisms. It discusses critical cell cycle regulators like cyclins and CDKs that form complexes to drive the cell cycle forward, as well as checkpoints that monitor cell growth and DNA integrity to ensure cells are ready to progress through the cycle. The cell cycle is tightly regulated by both intrinsic factors including cyclins and CDKs, and extrinsic factors like growth factors that influence division.
The cell cycle is the regulated process by which cells grow and divide to produce two daughter cells. It has two main phases: interphase and mitosis. Interphase consists of G1, S, and G2 phases where the cell grows and duplicates its DNA. Mitosis is when the cell divides. The cell cycle is regulated by cyclins, cyclin-dependent kinases (CDKs), and CDK inhibitors. Checkpoints ensure DNA quality and control cell cycle progression. Cell cycle dysregulation can lead to uncontrolled cell division and cancer.
Cell Cycle and Its Control Mechanism : Devendra KumarDevendra Kumar
The document provides an overview of the cell cycle and its control mechanisms. It discusses the different phases of the cell cycle including interphase (G1, S, G2 phases) and mitosis. It describes various checkpoints that monitor the cell cycle, including checkpoints at the G1/S transition and G2/M transition. Key regulators of the cell cycle include cyclins and cyclin-dependent kinases that promote phase transitions, as well as cyclin-dependent kinase inhibitors that inhibit transitions in response to errors or damage.
The cell cycle consists of four main phases - G1, S, G2, and M. In G1, cells grow and undergo protein synthesis in preparation for DNA replication. The S phase is when DNA replication occurs. In G2, the cell prepares for mitosis by producing necessary proteins. During mitosis (M phase), the nucleus and cell contents divide to form two daughter cells each with identical DNA. The progression through the cell cycle phases is regulated by cyclins and cyclin-dependent kinases (CDKs). Different cyclins activate specific CDKs to promote the transition between phases, with checkpoints ensuring errors are corrected before progression.
The document summarizes key aspects of cell cycle regulation. It discusses how experiments in the 1970s showed that the cytoplasm of mitotic cells contains factors that induce mitosis in non-mitotic cells, identifying maturation-promoting factor (MPF) as the key regulator. MPF consists of a catalytic subunit (Cdk) and a regulatory subunit (cyclin). Cyclin concentration varies throughout the cell cycle, activating Cdk at specific phases to drive progression. Precise phosphorylation of proteins by cyclin-Cdk complexes promotes cell cycle transitions through start and checkpoints.
The cell cycle is the ordered series of events that leads to cell division into two daughter cells. It consists of four main phases: G1, S, G2, and M. Checkpoints ensure each step is completed before progression. Cyclins activate CDKs at specific phases - G1 cyclins activate G1 CDKs which promote DNA replication by phosphorylating Rb and activating E2Fs. S-phase CDKs activate DNA replication origins. Mitotic CDKs promote mitotic events like spindle formation and chromosome condensation. Completion of mitosis involves chromosome segregation and cyclin degradation to inactivate CDKs and allow cell division.
Philippine Edukasyong Pantahanan at Pangkabuhayan (EPP) CurriculumMJDuyan
(𝐓𝐋𝐄 𝟏𝟎𝟎) (𝐋𝐞𝐬𝐬𝐨𝐧 𝟏)-𝐏𝐫𝐞𝐥𝐢𝐦𝐬
𝐃𝐢𝐬𝐜𝐮𝐬𝐬 𝐭𝐡𝐞 𝐄𝐏𝐏 𝐂𝐮𝐫𝐫𝐢𝐜𝐮𝐥𝐮𝐦 𝐢𝐧 𝐭𝐡𝐞 𝐏𝐡𝐢𝐥𝐢𝐩𝐩𝐢𝐧𝐞𝐬:
- Understand the goals and objectives of the Edukasyong Pantahanan at Pangkabuhayan (EPP) curriculum, recognizing its importance in fostering practical life skills and values among students. Students will also be able to identify the key components and subjects covered, such as agriculture, home economics, industrial arts, and information and communication technology.
𝐄𝐱𝐩𝐥𝐚𝐢𝐧 𝐭𝐡𝐞 𝐍𝐚𝐭𝐮𝐫𝐞 𝐚𝐧𝐝 𝐒𝐜𝐨𝐩𝐞 𝐨𝐟 𝐚𝐧 𝐄𝐧𝐭𝐫𝐞𝐩𝐫𝐞𝐧𝐞𝐮𝐫:
-Define entrepreneurship, distinguishing it from general business activities by emphasizing its focus on innovation, risk-taking, and value creation. Students will describe the characteristics and traits of successful entrepreneurs, including their roles and responsibilities, and discuss the broader economic and social impacts of entrepreneurial activities on both local and global scales.
Temple of Asclepius in Thrace. Excavation resultsKrassimira Luka
The temple and the sanctuary around were dedicated to Asklepios Zmidrenus. This name has been known since 1875 when an inscription dedicated to him was discovered in Rome. The inscription is dated in 227 AD and was left by soldiers originating from the city of Philippopolis (modern Plovdiv).
Level 3 NCEA - NZ: A Nation In the Making 1872 - 1900 SML.pptHenry Hollis
The History of NZ 1870-1900.
Making of a Nation.
From the NZ Wars to Liberals,
Richard Seddon, George Grey,
Social Laboratory, New Zealand,
Confiscations, Kotahitanga, Kingitanga, Parliament, Suffrage, Repudiation, Economic Change, Agriculture, Gold Mining, Timber, Flax, Sheep, Dairying,
This presentation was provided by Rebecca Benner, Ph.D., of the American Society of Anesthesiologists, for the second session of NISO's 2024 Training Series "DEIA in the Scholarly Landscape." Session Two: 'Expanding Pathways to Publishing Careers,' was held June 13, 2024.
Walmart Business+ and Spark Good for Nonprofits.pdfTechSoup
"Learn about all the ways Walmart supports nonprofit organizations.
You will hear from Liz Willett, the Head of Nonprofits, and hear about what Walmart is doing to help nonprofits, including Walmart Business and Spark Good. Walmart Business+ is a new offer for nonprofits that offers discounts and also streamlines nonprofits order and expense tracking, saving time and money.
The webinar may also give some examples on how nonprofits can best leverage Walmart Business+.
The event will cover the following::
Walmart Business + (https://business.walmart.com/plus) is a new shopping experience for nonprofits, schools, and local business customers that connects an exclusive online shopping experience to stores. Benefits include free delivery and shipping, a 'Spend Analytics” feature, special discounts, deals and tax-exempt shopping.
Special TechSoup offer for a free 180 days membership, and up to $150 in discounts on eligible orders.
Spark Good (walmart.com/sparkgood) is a charitable platform that enables nonprofits to receive donations directly from customers and associates.
Answers about how you can do more with Walmart!"
ISO/IEC 27001, ISO/IEC 42001, and GDPR: Best Practices for Implementation and...PECB
Denis is a dynamic and results-driven Chief Information Officer (CIO) with a distinguished career spanning information systems analysis and technical project management. With a proven track record of spearheading the design and delivery of cutting-edge Information Management solutions, he has consistently elevated business operations, streamlined reporting functions, and maximized process efficiency.
Certified as an ISO/IEC 27001: Information Security Management Systems (ISMS) Lead Implementer, Data Protection Officer, and Cyber Risks Analyst, Denis brings a heightened focus on data security, privacy, and cyber resilience to every endeavor.
His expertise extends across a diverse spectrum of reporting, database, and web development applications, underpinned by an exceptional grasp of data storage and virtualization technologies. His proficiency in application testing, database administration, and data cleansing ensures seamless execution of complex projects.
What sets Denis apart is his comprehensive understanding of Business and Systems Analysis technologies, honed through involvement in all phases of the Software Development Lifecycle (SDLC). From meticulous requirements gathering to precise analysis, innovative design, rigorous development, thorough testing, and successful implementation, he has consistently delivered exceptional results.
Throughout his career, he has taken on multifaceted roles, from leading technical project management teams to owning solutions that drive operational excellence. His conscientious and proactive approach is unwavering, whether he is working independently or collaboratively within a team. His ability to connect with colleagues on a personal level underscores his commitment to fostering a harmonious and productive workplace environment.
Date: May 29, 2024
Tags: Information Security, ISO/IEC 27001, ISO/IEC 42001, Artificial Intelligence, GDPR
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1. Chap. 19 The Eukaryotic Cell Cycle
Topics
• Overview of the Cell Cycle and Its Control
• Molecular Mechanisms for Regulating M & S Phase Events
• Mitogen-stimulated Entry of Cells into the Cell Cycle
• Surveillance Mechanisms in Cell-cycle Regulation
Goals
• Learn the roles of 1) cyclins and cyclin-
dependent protein kinases (CDKs), & 2)
ubiquitin-protein ligases in regulation of
the cell cycle.
• Learn the molecular mechanisms for
regulation of mitosis and S-phase events.
• Learn how mitogens propel quiescent cells
into the cell cycle.
• Learn how checkpoint mechanisms ensure
quality control in cell cycle events.
Cell division during C. elegans
early embryogenesis
2. Two fundamental processes occur with each cell cycle--
chromosomes replicate, and then they segregate equally to two
daughter cells. The mechanisms by which these processes occur
are similar in all eukaryotic cells. Processes occurring during the
cell cycle are highly regulated and coordinated. The cell cycle is
regulated primarily at the DNA replication and mitosis steps.
The master controllers of the cell cycle are 1) heterodimeric
protein kinases composed of a regulatory subunit (a cyclin) and
a catalytic subunit (a cyclin-dependent kinase, CDK), 2) two
ubiquitin-protein ligases, and 3) regulatory phosphatases.
Cyclin-CDKs phosphorylate and thereby regulate the activities
of numerous cell proteins that participate in replication and
division. The bound cyclins regulate the activities of the CDKs.
Ubiquitin-protein ligases participate in the timed destruction of
cyclins and other key proteins and thereby ensure passage
through the cell cycle is irreversible. In the absence of
regulation, cells replicate and divide uncontrollably, leading to
diseases such as cancer.
Overview of the Cell Cycle and Its Control
3. Regulating Protein Function by Degradation
The proteolytic degradation (turnover) of proteins is important for
regulatory processes, cell renewal, and disposal of denatured and
damaged proteins. Lysosomes carry out degradation of endocytosed
proteins and retired organelles.
Cytoplasmic protein degradation
is performed largely by the
molecular machine called the
proteasome. Proteasomes
recognize and degrade
ubiquinated proteins (Fig.
3.29). Ubiquitin is a 76-amino-
acid protein that after
conjugation to the protein,
targets it to the proteasome.
In ATP-dependent steps, the
C-terminus of ubiquitin is
covalently attached to a lysine
residue in the protein.
Polyubiquitination then takes
place. The proteasome
degrades the protein to
peptides, and released ubiquitin
molecules are recycling.
4. Major Events in the Cell Cycle
The cell cycle proceeds via four
phases in cycling (replicating)
somatic cells. These phases are
designated the G1, S, G2, and M
phases (Fig. 19.1). In G1 phase,
cells synthesize many of the
proteins that will be used for
DNA synthesis and chromosome
replication during S phase. G2
follows S and is a transitional
period preceding M phase. M
phase is a multistage period
wherein chromosomes separate
and the cell divides. In a dividing
mammalian cell, the four phases
of the cell cycle typically require
9 h, 10 h, 4.5 h, and 30 min
respectively. Many cells in adult
multicellular organisms do not
proliferate and never, or at least
rarely, divide. These cells exit
the cell cycle in G1 phase and
enter a quiescent phase called G0.
5. Review of M Phase Processes (I)
From an ultrastructural standpoint, M phase processes are the
most complex. In comparison, few changes are visibly apparent in
most cells during interphase, which consists of the combined G1,
S, and G2 phases. M phase is subdivided into 4 main periods--
prophase, metaphase, anaphase, and telophase (Fig. 18.36). In
prophase, replicated chromosomes condense and become visible.
In prometaphase, the nuclear membrane retracts and the mitotic
apparatus known as the spindle forms. Kinetochores assemble at
centromeres and attach the chromosomes to the mitotic spindle
fibers. In metaphase, chromosomes line up on the metaphase
plate in the center of the spindle.
6. Review of M Phase Processes (II)
In anaphase, sister chromatids of each duplicated chromosome
separate and are drawn toward the two spindle poles. Then in
telophase, the mitotic spindle disassembles, chromosomes
decondense, the nuclear envelope reforms surrounding the
chromosomes, and the cell undergoes cytokinesis--the physical
division of the cytoplasm.
7. Mechanism of Cell Cycle Regulation (I)
The molecular mechanisms by which the cell cycle is controlled
in a typical eukaryotic cell is presented in Fig. 19.30 below.
The initiation of the cell cycle occurs with the receipt of a
signal (e.g., a growth factor ligand) by a cell in G0 or G1. The
signal induces synthesis of G1 and G1/S phase cyclin-CDKs,
which then activate transcription of genes encoding DNA
synthesis enzymes and S phase cyclin-CDKs. S phase cyclin-
CDKs initially are held in check by inhibitors until G1/S phase
cyclin-CDKs phosphorylate the inhibitors. This triggers their
polyubiquitination by SCF ubiquitin ligase and degradation by
proteasomes. The released S phase cyclin-CDKs then
phosphorylate regulatory proteins bound to chromosomal
replication origins, promoting initiation of DNA synthesis. The
synthesis of mitotic cyclin-CDKs increases in S and G2 phases.
The activities of these complexes initially are blocked by
phosphorylation of CDK subunits, and then are activated later
by dephosphorylation. Once activated, mitotic cyclin-CDKs
phosphorylate a large number of proteins that control
chromosome condensation, retraction of the nuclear envelop,
formation of the mitotic spindle, and alignment of chromosomes
at the metaphase plate.
8. Subsequently, the anaphase promoting complex (APC/C), another
ubiquitin ligase, polyubiquitinates a protein called securin which
helps hold the sister chromatids of metaphase chromosomes
together. The degradation of securin by proteasomes initiates
anaphase and sister chromatids separate. Later in anaphase,
APC/C polyubiquitinates mitotic cyclins leading to their
degradation. Due to the loss of mitotic cyclin-CDK kinase activity
proteins responsible for chromosomal condensation, etc. are
dephosphorylated. Chromosomes then decondense, and nuclear
membranes are re-synthesized. Cells next move forward into
telophase where cytokinesis occurs, completing the cell cycle. In
the ensuing G1 phase, replication origin regulators are synthesized
and pre-replication complexes assemble at origins. This prepares
cells for another round of DNA synthesis in the next S phase.
Due to degradation of regulatory proteins at the G1/S,
metaphase/anaphase, and anaphase/telophase boundaries, the
passage of cells through the cell cycle is irreversible. The G1/S
transition (“START”) is a major checkpoint after which passage
through the cycle becomes independent of mitogens (e.g., growth
factors).
Mechanism of Cell Cycle Regulation (II)
10. APC/C Regulation of Sister Chromatid
Separation
Metaphase chromosomes are held together at centromeres via
ring-like proteins called cohesins (Fig. 18.36b, left). Once
spindle-assembly checkpoint processes have been satisfied (see
below), a protein called Cdc20 triggers sister chromatid
separation (Fig. 19.27 right). Cdc20 activates the APC/C
ubiquitin ligase which polyubiquitinates a protein called securin
which is an inhibitor of the enzyme called separase. Once
securin is degraded by proteasomes, separase cleaves the Scc1
component of cohesins resulting in their disassembly and
separation of sister chromatids to the spindle poles.
11. Regulation of Initiation of DNA
Replication by S phase Cyclin-CDKs (I)
In eukaryotic cells, DNA
synthesis occurs
simultaneously at multiple
replication origins which
initiate DNA synthesis
only once per cell cycle.
This ensures that the
number of chromosomes
per cell is correctly
maintained. At the end of
M phase when all M phase
cyclins are degraded, the
dephosphorylated forms of
MCM helicases and two
initiation factors assemble
along with the ORC
(origin recognition complex) at replication origins (Step 1, Fig.
19.19). Then when S phase cyclin-CDKs are activated at the end
of G1, S phase cyclin-CDKs and the DDK kinase phosphorylate
MCM helicases and the two initiation factors (Step 2).
Phosphorylation causes ORC and the two factors to disassemble.
12. Regulation of Initiation of DNA
Replication by S phase Cyclin-CDKs (II)
S-phase cyclin-CDKs also
phosphorylate MCM
helicase activators (red)
(Step 2). Subsequently,
origins are unwound by
active MCM helicases,
DNA polymerases load
onto the origins, and
bidirectional DNA
synthesis ensues (Step
3). The phosphorylated
forms of initiation
factors cannot rebind
DNA at origins, and they
are degraded by the SCF
proteasome. Only after S
phase and mitotic cyclin-CDKs are degraded at the end of
mitosis can the initiation factors be synthesized and accumulate
in their dephosphorylated states, and then assemble again at
replication origins. This ensures that DNA replication occurs
only once per cell cycle.
13. Mitogen-stimulated Gene Expression in
G0-arrested Mammalian Cells
Cells in G0 do not synthesize cyclins or CDKs. The transition
of quiescent cells from G0 to G1 and resumption of the cell
cycle is triggered by growth factors in serum (mitogens).
Shortly after binding to receptors, growth factors turn on
the transcription of early response genes using TFs that
preexist in the cell. Among the early response genes are c-
fos, c-jun, and c-myc These genes turn on the transcription
of delayed-response genes. Included within the latter are the
G1 cyclin-CDKs and a TF called E2F, which is controlled by
the Rb gene (next slide). The synthesis of G1 cyclin-CDKs
propels the cell into G1. Prior to the START point, the
withdrawal of growth factors leads to rapid degradation of G1
cyclin-CDKs and return to G0. At the restriction point, G1
cyclin-CDKs reach irreversibly high levels and cells are
committed to enter S phase. After the restriction point,
growth factors are no longer needed for completion of the
cycle. One role of TGFß is inhibition of G1 cyclin-CDKs.
14. Rb and the START Point
Rb is the prototype tumor suppressor gene. Inactivation of Rb
leads to tumors of the retina in children. Rb also is inactivated
in many other tumors. In non-proliferating cells, Rb protein
binds to E2F, and the complex activates histone deacetylases
leading to gene silencing (Fig. 19.15b). When the expression of
the G1 cyclin-CDKs (cyclin D-CDK4/6) are turned on by a
mitogen, Rb is phosphorylated and active E2F is released. E2F
activates transcription of genes needed for passage into S
phase, namely genes encoding DNA synthesis enzymes, Cyclins E
& A (G1/S phase cyclins), CDK2, and
itself. Cyclins E/A-CDK2 (G1/S
cyclin-CDKs) also phosphorylate Rb.
This occurs even if the mitogen is
withdrawn and is the key control
allowing the cell to pass through the
restriction point. In S, G2, and
mitosis, S-phase and mitotic cyclin-
CDKs continue to phosphorylate Rb.
Only after degradation of mitotic
cyclins at the end of mitosis is Rb
dephosphorylated. Rb then can
inhibit E2F in early G1 and in G0-
arrested cells.
15. Checkpoints in Cell-cycle Regulation
To minimize mistakes in
cell cycle events and
transmission of damaged
DNA or otherwise
abnormal chromosomes
to daughter cells,
numerous quality control
checkpoints regulate
passage of cells through
the cell cycle. For
example, DNA-damage
checkpoints occur at
several steps (Fig.
19.34). If damage is
detected, the cell cycle
is arrested and the
damage repaired, if
possible. Severe DNA
damage may trigger
apoptosis (Chap. 21).
16. The Spindle-assembly Checkpoint
In nondisjunction, chromosomes segregate in anaphase prior to
attachment of the kinetochores of all sister chromatids to mitotic
spindle fibers. This results in unequal segregation of chromosomes
to daughter cells (below left). In trisomy 21, nondisjunction occurs
95% of the time in meiosis I during gametogenesis in the mother.
To prevent nondisjunction, a regulatory mechanism involving the
Mad2 protein which is known as the spindle-assembly checkpoint
operates just prior to anaphase (Fig. 19.35). Mad2 binds to
kinetochores that have not bound to microtubules of the mitotic
spindle. Kinetochore binding activates Mad2, and it in turn inhibits
the activity of Cdc20 which controls the APC/C ubiquitin ligase (Fig.
19.27). This delays degradation of securin and anaphase. Only
after all kinetochores have bound to the spindle is Mad2
inactivated, releasing Cdc20 to trigger securin degradation.