Pranjali Saxena

In cel cycle there are two phases interphase and m phase and further interplase divide in 3 part and...

The cell cycle is a series of events that cells go through as they grow and divide. It consists of two main phases: 1. Interphase (The cell’s preparation time) Interphase is the longest phase of the cell cycle and is divided into 3 parts: a) G₁ Phase (Gap 1): What happens? The cell grows larger. Organelles duplicate. Proteins and enzymes needed for DNA replication are made. Checkpoint: The cell checks whether it has enough nutrients and enzymes to proceed. b) S Phase (Synthesis): What happens? DNA replication occurs. Each chromosome makes a copy of itself (sister chromatids), doubling the DNA content. Important: The cell now has two identical sets of chromosomes. c) G₂ Phase (Gap 2): What happens? Final preparations for division. The cell checks the copied DNA for errors. More proteins are made (especially for spindle formation). Checkpoint: Ensures all is ready for mitosis. 2. M Phase (Mitosis + Cytokinesis) This is the phase where the cell divides. It has two major parts: Mitosis (Division of the nucleus) Cytokinesis (Division of the cytoplasm) Mitosis is divided into 4 stages: a) Prophase: What happens? Chromatin condenses into visible chromosomes. Each chromosome consists of 2 sister chromatids joined at a centromere. The nuclear membrane starts to break down. Spindle fibers begin to form from the centrosomes. b) Metaphase: What happens? Chromosomes line up at the center (equator) of the cell (called the metaphase plate). Spindle fibers attach to the centromeres of the chromosomes. c) Anaphase: What happens? The centromeres split. Sister chromatids are pulled apart toward opposite poles of the cell by the spindle fibers. Now, each chromatid is considered an individual chromosome. d) Telophase: What happens? Chromosomes reach the poles and start to decondense back into chromatin. Nuclear envelopes reform around each set of chromosomes. Spindle fibers disappear. Now, there are two nuclei in one cell. Cytokinesis (after Mitosis): What happens? The cytoplasm divides, and two genetically identical daughter cells are formed. 🎯 Summary Table: Phase Key Activity G₁ Cell growth, organelles duplicate S DNA replication G₂ Preparation for mitosis, error checking Prophase Chromosomes visible, spindle forms, nucleus breaks Metaphase Chromosomes line up at the center Anaphase Chromatids separate to opposite poles Telophase Two nuclei reform, chromosomes uncoil Cytokinesis Cytoplasm divides, two daughter cells form