हिंदी माध्यम • NCERT लाइन-दर-लाइन विश्लेषण
NEET 2026 / 2027
NEET Biology Class 11 Chapter 10: कोशिका चक्र और कोशिका विभाजन (Cell Cycle in Hindi)
S-Phase क्रोमोसोम ट्रैप, Anaphase 4n=92 विश्लेषण और 3 चेकपॉइंट्स • टॉपर्स हस्तलिखित नोट्स
⚠️ S-Phase का सबसे बड़ा भ्रम (Examiner's Trap)
S-Phase में DNA की मात्रा 2C से बढ़कर 4C हो जाती है, लेकिन गुणसूत्रों (Chromosomes) की संख्या 2n = 46 ही रहती है। दोनों सिस्टर क्रोमैटिड्स एक ही सेंट्रोमियर से जुड़े रहते हैं।
⚡ गोल्डन फॉर्मूला: गुणसूत्रों की संख्या = सेंट्रोमियर की संख्या!
| Cell Cycle Phase | DNA Content | Chromosome Count | Ploidy State |
|---|---|---|---|
| G1 Phase | 2C | 46 (2n) | Diploid (2n) |
| S Phase (Synthesized) | 4C (Doubled!) | 46 (STAYS 2n!) ✅ | Diploid (2n) |
| G2 Phase | 4C | 46 (2n) | Diploid (2n) |
| Anaphase (Centromere Split) | 4C | 92 (Temporary 4n) ⚡ | Tetraploid (4n) |
| Telophase / Cytokinesis | 2C per daughter cell | 46 (2n) per cell | Diploid (2n) |
🚦 The 3 Critical Cell Cycle Checkpoints (NEET PYQ Favorite)
- 1. G1/S Restriction Gate: Controlled by Cyclin D + CDK 4/6. Phosphorylates Rb protein. Once crossed, the cell is committed to divide.
- 2. G2/M Integrity Gate: Regulated by Cyclin B + CDK 1 (MPF). Sensed by p53 tumor suppressor. Halts division if DNA is damaged.
- 3. M-Phase SAC Gate (Spindle Assembly): Senses kinetochore tension before anaphase. Prevents nondisjunction and aneuploidy.
⏱️ Video Timestamps & Key Moments:
00:00 - S-Phase Fallacy (DNA 2C se 4C, 2n=46)
00:15 - Master Ploidy Matrix & Anaphase Cleavage
00:32 - 3 Critical Cell Cycle Checkpoints (G1/S, G2/M, SAC)
00:46 - NEET Handwritten Notes Vault & Qbnexa Store
00:15 - Master Ploidy Matrix & Anaphase Cleavage
00:32 - 3 Critical Cell Cycle Checkpoints (G1/S, G2/M, SAC)
00:46 - NEET Handwritten Notes Vault & Qbnexa Store
📚 NEET PCB Handwritten Notes Vault (83 Chapters)
Line-by-line NCERT visual mindmaps, 500+ examiner traps, and classified PYQs for Class 11 & 12 Physics, Chemistry, and Biology.
👉 Explore the Store Window