Cell cycle and its Regulation Presentation PPT.
- 1. CELL CYCLE AND IT’S REGULATION PRESENTED BY: GANGAD SAKSHI GORAKHNATH F.Y.M.PHARM(PHARMACOLOGY) GUIDED BY: DR.S.B DIGHE HEAD OF PHARMACOLOGY DEPARTMENT
- 2. The cell never acts; it reacts --Ernst Haeckel
- 3. INTRODUCTION • Cell is structural and functional unit of life. • Cell division is a very important process in all living organisms • Cell cycle was described by Howard and Pele in 1953. • Cell cycle is defined as the stages through which a cell passes from one cell division to the next. During this phase the cell grows and prepares for the division.
- 4. • Completes in 2 phases (I) Interphase– Preparatory phase, divided into 3 sub phases (i) G1 (GAP 1) phase (ii) S (Synthesis) phase (iii) G2 (GAP 2) phase (II) M phase– Phase of division, divided into 2 sub phases (i) Karyokinesis (Nuclear division)– divided into 4 sub phases (a) Prophase (b) Metaphase (c) Anaphase (d) Telophase (ii) Cytokinesis (Division of cytoplasm)
- 6. (I) INTERPHASE • Generally cell biologists divide interphase into two gap phases (G1 and G2) synthetic or S phase . 1. G1 Phase: • G1 or Gap phase1 is the first stage of interphase in which cells grow and resumes RNA and protein synthesis. • It is the primary growth phase of the cell cycle. • The cell is metabolically active and continuous cell growth.
- 7. 2. S Phase: The G1 phase is followed by S or synthetic phase in which chromosomal DNA is replicated. Each chromosome produces two daughter • DNA synthesis and replication • Centrioles duplicate
- 8. 3. G2 Phase: • G2 or Gap phase 2 is another period of growth. • There is an increase in transcription and protein synthesis that essentially prepares the cell for the mitotic phase. • The number of organelles like mitochondria grows and divides to double their numbers.
- 9. 4. Go Phase • It is initial stage cell are metabolically active but not proliferate. • Sometimes , cells are Not divided they doesn’t goes to a S Phase. They goes to inactive stage.
- 10. (II) MITOSIS PHASE • Mitosis separates the replicated sister chromatids. It is divided into six phases namely prophase, prometaphase, metaphase, anaphase, telophase and cytokinesis.
- 11. 1. Prophase The chromatin material that is condensed is called chromosomes. • Each chromosome contains two chromatids. Which are attached with centromers • Centromers are present at opposite poles inside the cell. • Chromosomes form microtubules. These microtubules along with chromosomes are called Aster. • These microtubules form a thread-like structure called spindle fiber.
- 12. 2. Metaphase • The spindle fibers are attached to the kinetochore • Kinetochore attracts the chromosomes and places them in an equilateral plane
- 13. 3. Anaphase • The separation of sister chromatids begins at anaphase. • Sister chromatids are pulled to opposite sides of the cell. • The movement of the chromosomes to the opposite poles of the spindle is known as anaphase movement.
- 14. 4. Telophase • Is the final stage of mitosis and by this time all chromosomes have arrived at the spindle poles. • The chromosomes become decondensed and resume transcription, the nucleolus reappears and form the nuclear membrane, ER and the Golgi body. • The organelles that were doubled and distributed equally to both cells. Each daughter cell receives a copy of genetic material.
- 15. 5. Cytokinesis • It is the division of cytoplasm that results in two daughter cells with identical genetic material.
- 16. REGULATORY MOLECULES OF THE CELL CYCLE The cell cycle is controlled by proteins to ensure that cells divide correctly. • Cyclins and Cyclin-Dependent Kinases (CDKs): Cyclins are proteins that bind to CDKs to activate their kinase activity. • Different cyclins are present at specific points in the cycle: • Cyclin D: Activates CDK4 and CDK6 to push the cell through the G1 phase. • Cyclin E: Activates CDK2 to help the cell transition from G1 to S phase. • Cyclin A: Activates CDK2 during the S phase for DNA replication. • Cyclin B: Activates CDK1 to initiate mitosis.
- 18. CELL CYCLE CHECKPOINT G1 Checkpoint: Checks for DNA damage and ensures that conditions are favorable for DNA replication. G2 Checkpoint: Verifies that DNA replication has occurred correctly and that the cell is ready for mitosis. • Metaphase Checkpoint: Ensures that all chromosomes are properly attached to the spindle fibers before proceeding to anaphase.