Mitosis
மைட்டாசிஸ்
Mitosis is not just cell division; it is the biological guarantee of genetic continuity. If your somatic cells failed to maintain the exact diploid chromosome number, you would cease to exist as a functional organism. Do not confuse this with Meiosis, where the ploidy is halved.
The idea
Mitosis is an equational division resulting in two daughter cells identical to the parent cell. It proceeds through four distinct stages: Prophase, Metaphase, Anaphase, and Telophase. The process ensures that the chromosome number remains conserved, maintaining genetic stability across generations of somatic cells. It is the fundamental mechanism for growth and tissue repair in multicellular organisms.
Why it matters
It exists to maintain genetic consistency across cell generations and to restore the nucleo-cytoplasmic ratio disturbed by cell growth.
NEET lens
NEET focuses on the movement of chromosomes and the behavior of the spindle apparatus. Memorize the specific events of Anaphase, as it is the most frequently tested stage. Watch out for questions distinguishing between mitosis in plants and animals, specifically cytokinesis. Expect at least one question on the significance of equational division.
Clinical significance
Uncontrolled mitosis is the hallmark of cancer. When the cell cycle checkpoints fail, cells divide indefinitely, forming tumors. Conversely, failure of mitosis in bone marrow leads to severe anemia and immune deficiency.
Introduction
Mitosis is nuclear division producing two daughter cells genetically identical to the parent, maintaining the chromosome number (2n → 2n). It underlies growth, repair, and asexual reproduction.
Core concept
PMAT stages: Prophase — chromatin condenses, spindle forms, nuclear envelope breaks down. Metaphase — chromosomes align at metaphase plate (most condensed, best for karyotyping). Anaphase — centromeres split, sister chromatids pulled to opposite poles by spindle fibers. Telophase — nuclear envelope reforms, chromosomes decondense. Then Cytokinesis: plant cells form cell plate (from Golgi vesicles); animal cells form cleavage furrow (actin-myosin ring).
Go deeper
Spindle assembly checkpoint (SAC): activated by any unattached kinetochore — releases Mad2 protein → inhibits APC/C → cohesin not cleaved → chromatids cannot separate. This ensures every chromosome attaches to spindle before anaphase begins. Failure → chromosome missegregation → aneuploidy → cancer.
From Class 10
For growth and repair, cells need to produce exact copies of themselves. Mitosis is the process that creates two genetically identical daughter cells.