Cell division and mitosis

Understand the idea

Cell division makes new cells for growth, replacement, and reproduction. Unicellular organisms often split by binary fission. Multicellular bodies use mitosis for new body cells and meiosis for sperm and egg. Mitosis copies chromosomes so each daughter cell matches the parent. In humans that number stays 46.

The cell cycle is G1 (growth), S (DNA and centrosome copied), G2 (more growth and checks), then M phase. Interphase is G1 + S + G2, when the cell is not yet visibly dividing. M phase is prophase, metaphase, anaphase, telophase, then cytokinesis, which splits the cytoplasm.

In prophase the nuclear envelope breaks, the nucleolus fades, and chromosomes condense as sister chromatids. Prometaphase attaches spindle fibres to kinetochores. Metaphase lines chromosomes at the equator. Anaphase pulls sisters apart. Telophase rebuilds nuclei. Animals pinch in; plants build a cell plate.

What to remember

• Mitosis → two identical body cells; chromosome number unchanged.
• Cycle: G1, S, G2, mitosis, cytokinesis.
• PMAT + cytokinesis completes the visible division.

Recap

Mitosis keeps chromosome number and identity. Learn the cycle names, then PMAT, then how plant and animal cells finish cytokinesis differently.