NEET 2025 Biology - Cell Cycle L2 PDF

# NEET 2025 BIOLOGY - NEW NCERT 360 - CELL CYCLE & CELL DIVISION - PART 2 ## ** CELL DIVISION ** * **46** * **2n, 2c** * **8** * **46** * **2n, 2c** * **8** * **MEIOSIS** - **Reductional Division** * **MITOSIS** * **...

# NEET 2025 BIOLOGY - NEW NCERT 360 - CELL CYCLE & CELL DIVISION - PART 2 ## ** CELL DIVISION ** * **46** * **2n, 2c** * **8** * **46** * **2n, 2c** * **8** * **MEIOSIS** - **Reductional Division** * **MITOSIS** * **8** * **2n, 2c** * ** (46)** * **8** * **2n, 2c** * ** (46)** * **23** * **23 23 23 23** * **n, c n, c n, c n, c** ## ** COMPLETE BIOLOGY BY SEEP PAHUJA (NEET UG)** **G1 - S - G2 - Meiosis I - M phase** **INTER PHASE** * **2n, 2c** * **8 => 8 => 8** * **46 => 46 => 46** **Meiosis I** * **P → Prophase I → PD** * **M → Metaphase I → MD** * **A → Anaphase I → AD** * **T → Telophase I → TII** **Inter Kinesis / Intra-Meiotic phase** * **RNA formation** * **Protein** * **Centriole duplication** **PROPHASE I** * **Leptotene** * Condensation starts * Ends of chromosome not distinct * **BOUQUET STAGE** * **Zygotene** * **Synapsis** (Pairing of homologous chromosomes) * **Synaptonemal Complex** * **TETRAD** (Nucleo protein complex) * **BIVALENT** * No. of Bivalents = 23 * 8 - **UNIVALENT**, **DIAAD** * **Pachytene** * Tetrad starts appearing * **CROSSING OVER** / RECOMBINATION * Genetic exchange of homologus chromosomes * Non - sister chromatid of homologous chromosomes * Enzyme - **Recombination Complex** * **Nodule** * **E → RECOMBINASE** * **Diplotene** * Dissolution of *Synaptonemal Complex* * **X - Shaped** * **CHIASMATA** * Diplotene gets arrested for months to years (Human female) * **Dictyotene** * **Diakinesis** * **Terminalisation of CHIASMATA** * Nuclear membrane, nucleolus, organelles disappear **METAPHASE I** * Homologous chromosomes align at **equatorial plate** * **Random** * 2 metaphasic plate * No of spindle fibers = 46 **ANAPHASE I** * Separation of homologous chromosomes * **Reduction** of no of chromosomes **TELOPHASE I** * Nuclear membrane, nucleolus, organelles reappear * 23 chromosomes * 46 chromatid * **Decondensation** **Meiosis I** * **46 8 8** * **23 23** * **Reductional Division** ## **After Cytokinesis** * **8 8 8 8** * **23 n, c , 23 n, c, 23 n, c, 23 n, c** * **10pg, 10pg, 10pg, 10pg** ## **Beyond NCERT** * **MITOGENS** → **Promote Mitiosis** * Eg: Insulin, Cytokinin/Auxin * **MITOTIC POISON** → **Inhibit Mitosis** * Eg: RNase, Mustard gas, **COLCHICINE** → Inhibit spindle formation ## **Conservation of chromosome in sperm** * **46 46** * **23 23 23** * **Egg** - **46** * **92** ## **MEIOSIS II** → **Same as MITosis** * **23 8 8** * **PROPHASE II** * **METAPHASE II** * 1 metaphasic plate * Spindle fibers = 46 * 23 chromosomes align at 1 metaphasic plate * **ANAPHASE II** * Splitting of centromere * Chromatid separates * **TELOPHASE II** * **8 8** * **23 n, c** * **23 n, c** * **CHROMATID = 23** * Complete decondensation of chromosomes **Parent Cell - 46 chr - 20pg** **Meiosis I** * **G1 → S → G2** * **No of chromosomes** / **No of chromatids** / **DNA content** * **G2** * **46 → 92 → 40pg** * **Telophase I - per cell** * **46 → 92 → 40pg** * **per nucleus** * **23 → 46 → 20pg** ## **Meiosis II** * **No of chromosomes** / **Chromatids** / **DNA content** * **PROPHASE I** * **23 n, c** → **46** → **20pg** * **METAPHASE I** * **TELOPHASE I - per cell** * **46 → 46 → 40pg** * **per nucleus** * **23 n, c** → **23** → **10pg** ## **COMPLETE BIOLOGY BY SEEP PAHUJA (NEET UG)**