CELL-CYCLE_20250703_231927_000 biology0.pptx

general bioloogy

1. CELL CYCLE Prepared by: Angel C. Dagohoy Stage 1 to stage 2

2. S TAGE 1: I NTERPHASE Interphase is the growth period in the cell cycle characterized by cell preparation by replication of it's genetic information and all of it's organelles.

3. THREE MAIN PARTS OF INTERPHASE GAP 1 (G₁) PHASE > Cell carries out it's normal metabolic functions (examples: during G1 phase, an intestinal cell performs its primary duty to absorb nutrients) > Cells increase their size > Cell prepares for DNA synthesis  SYNTHESIS (S) PHASE > DNA synthesis (replication) occurs; cells make a copy of it's genetic material in the form of nuclear DNA > Cells spend considerable amount of time and energy to make couples of it's chromosomes  > Cells continue to carry out their normal functions and also undergo further growth and synthesis of DNA and proteins. > This stage contains critical "checkpoint" before transitioning to the next stage which is the cellular division GAP 2 (G₂) PHASE

4. STAGE 2: CELLULAR DIVISION: MITOSIS AND MEIOSIS Some cells stop dividing and enter a resting stage called G₀ (Gap Zero). In G₀, cells do not divide but still carry out their functions. Examples : Neuron cells and heart muscle cells – highly specialized and hard to replace. Immune cells that are needed at a later time, such as lymphocytes can stay in G₀ for years until needed.They re-enter the cycle and divide rapidly when they detect an infection.

5. CELL CYCLE CHECKPOINTS In order to prevent mutations/chromosomal aberrations and ensure major events occur at correct times , several cell cycle checkpoints are present at various times in the cycle preventing cells from proceeding to the next stage unless all criteria had been met. "Checkpoints or control points" are moments when the cell can "check" it's internal conditions and "decide" whether to progress to the next phase or remain. It is similar to what happens during a police operation checkpoint. When you have met the requirements asked by the police officer in-charge, you can go pass the checkpoint

6. > Restriction point to enter S phase
> Checks DNA damage and favorable conditions
> Availability of growth factors
> G1 checkpoint can direct cell into quiescene (Go) if conditions are not favorable  > Checks for DNA damage before/during replication
> Prevents reduplication of DNA THE MAIN ACTIVITIES DONE DURING CELL CHECKPOINT G₁ CHECKPOINT S CHECKPOINT

7. > Allows entry into mitosis
> Checks DNA damage
> Ensures DNA is duplicated  > During mitosis: allows entry to anaphase
> Ensures all chromosomes alliged at metaphase plate and attached to the spindle fiber THE MAIN ACTIVITIES DONE DURING CELL CHECKPOINT G₂ CHECKPOINT M CHECKPOINT

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