Control of cell cycle

INTRODUCTION
Definition
history
DIFFERENT PHASE
G0 PHASE
INTERPHASE
M PHASE
CHECKPOINT
HOW DOES IT WORK
Inhibitors
Mechanism of action
Function
CONCLUSION
references

1. Control of cell cycle By KAUSHAL KUMAR SAHU Assistant Professor (Ad Hoc) Department of Biotechnology Govt. Digvijay Autonomous P. G. College Raj-Nandgaon ( C. G. )

2. Control of cell cycle synopsis INTRODUCTION Definition history DIFFERENT PHASE G0 PHASE INTERPHASE M PHASE CHECKPOINT HOW DOES IT WORK Inhibitors Mechanism of action Function CONCLUSION references

3. Introduction “Where the cell arises there must be a previous cell, just an animal arise from only animal and Plants from only plants” It was proposed by German pathologist Rudolf Virchow in 1858,carried with it a profound Massage continuity of life.

4. The cell cycle , or cell-division cycle , is the series of events that takes place in a cell leading to its division and duplication (replication). The cell-division cycle is a vital process by which a single-celled fertilized egg develops into a mature organism. The whole process is highly regulated by control system of cell cycle .

5. The molecular events that control the cell cycle are ordered and directional; that is, each process occurs in a sequential fashion and it is impossible to "reverse" the cycle.. fig. overview of cell cycle

6. Definition “ The network of proteins that regulate DNA synthesis (G1/S), mitotic entry (G1/M), and mitotic exit is referred as regulation or control of Cell cycle.” history Cell cycle is divided into 4 phases G1,G2,S, mitotic phase by “ howard &pale in 1953. Cyclin was discoved by Evans et al in 1983.

7. Different phases The cell cycle consists of four distinct phases: G phase G 1 phase S phase G 2 phase M phase Mitosis -In which the cell's , CHROMOSOME are divided between the two daughter cells. Cytokinesis- , in which the . cell's CYTOPLSAM divides in Half forming distint cells.

8. Fig. Different phases of cell cycle

9. FIGURE 1-17 During growth, eukaryotic cells continually progress through the four stages of the cell cycle, generating new daughter cells.

10. Checkpoint “A checkpoint in the cell cycle is a critical control point where stop and go signals regulate the cell cycle.” Three major checkpoints are found in the G1, G2 and M phases.

11. How does it works Checkpoints are especially important as points in the cell cycle where the control system can be regulated by signals from other cells. T he cell-cycle control system triggers the events of the cycle in a specific order. If one of the steps is delayed, the control system delays the activation of the next steps so that the normal sequence is maintained.

12. Cell cycle control system

13. The cell-cycle control system governs the cell-cycle machinery by cyclically activating and then inactivating the key proteins and protein complexes that initiate or regulate DNA replication, mitosis, and cytokinesis . The cell cycle checkpoints made up of composites of protein kinases and adaptor proteins that all play salient roles in the maintenance of the integrity of the division .

14. Check points Depends on Cyclically Activated Protein Kinases

15. The protein kinases that are part of the core of the cell-cycle control system are present in proliferating cells throughout the cell cycle. They are activated, however, only at appropriate times in the cycle, after which they quickly become deactivated again. Thus, the activity of each of these kinases rises and falls in a cyclical fashion. Some of the protein kinases become active toward the end of G1 phase and are responsible for driving the cell into S phase.

16. Another kinase becomes active just before M phase and is responsible for driving the cell into mitosis. Switching these kinases on and off at the appropriate times is partly the responsibility of a second set of protein components of the control system—the cyclins

17. Different Cyclin–Cdk Complexes Trigger Different Steps in the Cell Cycle

18. INHIBITOR Families of genes, the cip/kip family ( CDK interacting protein/Kinase inhibitory protein ) prevent the progression of the cell cycle. Because these genes are instrumental in prevention of tumor formation, they are known as tumor suppressors. The cip/kip family includes the genes p21, p27 and p57. They halt cell cycle in G 1 phase, by binding to, and inactivating, cyclin-CDK complexes. p21 is activated by p53 (which, in turn, is triggered by DNA damage e.g. due to radiation). p27 is activated by Transforming Growth Factor β (TGF β), a growth inhibitor .

19. Fig-DNA damage arrests cell cycle at G1 PHASE

20. Function An important function of many checkpoints is to assess DNA damage, which is detected by sensor mechanisms. The DNA damage checkpoint is always active. When damage is found, the checkpoint uses a signal mechanism . All the checkpoints that assess DNA damage appear to utilize the same sensor-signal- effector mechanism.

21. DNA replication and chromosome distribution are indispensable events in the cell cycle control . The checkpoints are quality control of the genome to maintain genomic integrity . What happens if one of the checkpoint is lost ?

22. Checkpoint failure often causes mutations and genomic arrangements resulting in genetic instability. Genetic instability is a major factor of birth defects and in the development of many diseases, most notably cancer. A disregulation of the cell cycle components may lead to tumor formation

23. "Chapter 14: The Eukaryotic Cell Cycle" 2. “Cell and molecular biology“ by Gerald karp 6 th edition Cooper GM (2000). 3. “Molecular cell biology” by lodish 5 th edition Web site www.google.com Wikipedia, the free encyclopedia References