Cell cycle in relation to cell regulations and apoptosis

Cell cycle

1. CELL CYCLE The cell cycle is a critical process through which a cell grows and divides to produce two daughter cells. It plays an essential role in growth, tissue repair, and reproduction in living organisms . In many biological systems, the regulation of the cell cycle is closely tied to programmed cell death, also known as apoptosis. This balance between cell division and death ensures tissue homeostasis and prevents the development of diseases such as cancer. The cell cycle can be broken down into several phases, and any disruption in these phases can trigger apoptosis (Jones & Patel, 2023).

2. DIAGRAM AND MORPHOLOGY OF CELL CYCLE

3. Interphase Interphase is a period where the cell grows and prepares for division. It is composed of the G1, S, and G2 phases, during which the cell increases in size, duplicates its DNA, and synthesizes the proteins necessary for mitosis. Apoptosis can be triggered if errors occur in these processes or if the cell's DNA is irreparably damaged. G1 Phase (Gap 1): In this stage, the cell undergoes rapid growth and performs its normal functions. It produces proteins and other molecules necessary for DNA replication and future cell division. This phase includes a checkpoint to ensure the environment is favorable for cell division. but if it detects significant damage or lacks nutrients, it can activate apoptotic pathways to prevent propagation of defective cells ( Alberts et al., 2023).

4. CONT… S Phase (Synthesis): DNA replication occurs here, resulting in the duplication of genetic material. Each chromosome is replicated into two sister chromatids, held together at the centromere. G2 Phase (Gap 2): The cell continues to grow and synthesize proteins that are critical for mitosis, such as microtubules. At the G2 checkpoint, the cell verifies that DNA replication is complete and free of errors.

5. MITOSIS Mitosis is the stage of active cell division where the cell’s replicated DNA is distributed into two daughter cells. The cell must tightly regulate mitosis, as errors in this process can lead to aneuploidy, a condition where cells have an abnormal number of chromosomes, which can trigger apoptosis. Mitosis consists of several distinct sub-stages : Prophase: Chromosomes condense into visible structures. The nuclear membrane disintegrates, and the mitotic spindle begins to form from the centrosomes. If DNA damage or improper chromosome condensation is detected, the cell may initiate apoptosis through checkpoints.

6. CONT… Metaphase: Chromosomes align at the metaphase plate, an imaginary central line, ensuring that each daughter cell will receive one complete set of chromosomes. Anaphase: Sister chromatids are pulled apart and move toward opposite poles of the cell. At this stage, the chromatids are referred to as individual chromosomes. Telophase : Chromosomes arrive at the opposite poles, and the nuclear membranes begin to reform around each set of chromosomes. The chromosomes de-condense into chromatin

7. CYTOKINESIS Cytokinesis divides the cytoplasm, forming two genetically identical daughter cells. In animal cells, a contractile ring forms the cleavage furrow, which pinches the cell in two. In plant cells, a cell plate forms at the center, which eventually becomes part of the cell wall. Errors in cytokinesis can lead to multinucleated cells, a condition that may trigger apoptosis. Regulation of the Cell Cycle The cell cycle is controlled by a series of checkpoints and proteins such as cyclins and cyclin -dependent kinases (CDKs). These regulatory proteins ensure that the cell only progresses to the next phase when the previous phase has been completed correctly. The G1 checkpoint monitors the cell size, nutrient levels, and DNA integrity. If conditions are not ideal, the cell can enter a quiescent state called G0 (Miller et al., 2022). The G2 checkpoint ensures that DNA replication is complete and that there are no errors before mitosis

8. REFERENCES Alberts , B., Johnson, A., Lewis, J., Raff, M., Roberts, K., & Walter, P. (2023). Molecular Biology of the Cell (7th ed.). Garland Science. Jones, C. J., Patel, R. T., & Morgan, F. (2023). "Cytokinesis Mechanisms in Plant and Animal Cells." Cell and Tissue Research, 18(5), 145-158. Miller, D. S., Clark, A., & Baker, N. (2022). " Cyclins and the G1 Checkpoint." Cell Cycle Research, 23(2), 112-123.