NEET Biology NCERT Line-by-Line Breakdown: High-Yield Genetics & Human Physiology Notes
In NEET UG, Biology carries 360 marks out of 720 (50% of the entire paper). Over the last five exam cycles (2020–2025), analysis shows that 98% of Biology questions are extracted directly from NCERT sentences, diagram labels, and chapter summary footnotes.
Scoring 340+ in Biology is the mandatory threshold for securing an MBBS seat in a premier Government Medical College (GMC). This guide provides a line-by-line breakdown of the two highest-yield units: Genetics & Evolution (15–18 questions) and Human Physiology (12–15 questions).
1. Unit VII: Genetics & Molecular Basis of Inheritance
Together, Principles of Inheritance and Variation and Molecular Basis of Inheritance constitute the single largest question bank in NEET Biology, accounting for up to 72 marks.
A. Core NCERT Facts: Principles of Inheritance
- Mendel's True-Breeding Lines: Mendel conducted artificial pollination/cross-pollination experiments on 14 true-breeding pea plant varieties (7 pairs of contrasting traits).
- Incomplete Dominance vs. Co-dominance:
- Incomplete Dominance: Antirrhinum majus (Snapdragon/Dog flower) phenotypic and genotypic ratio in F2 is 1:2:1 (Red:Pink:White).
- Co-dominance: Human ABO blood grouping determined by gene I with three alleles ($I^A$, $I^B$, $i$). Alleles $I^A$ and $I^B$ produce different sugars; $i$ produces none.
- Linkage and Recombination (T.H. Morgan):
- Morgan used Drosophila melanogaster (fruit fly) because they complete life cycles in 2 weeks and produce clear sexual dimorphism.
- Genes yellow body (y) and white eyes (w) showed 1.3% recombination (tight linkage).
- Genes white eyes (w) and miniature wings (m) showed 37.2% recombination (loose linkage).
- Alfred Sturtevant used recombination frequency to construct genetic maps (1% recombination = 1 map unit or centimorgan).
B. Core NCERT Facts: Molecular Basis of Inheritance
- Dimensions of DNA:
- Double helix pitch = 3.4 nm (34 Angstroms).
- Distance between consecutive base pairs = 0.34 nm ($0.34 imes 10^{-9}$ m).
- Approximately 10 base pairs per turn.
- Length of DNA in typical human diploid cell = $6.6 imes 10^9 ext{ bp} imes 0.34 imes 10^{-9} ext{ m} = 2.2 ext{ meters}$.
- Central Dogma & Meselson-Stahl Experiment:
- Semi-conservative replication proven in E. coli using heavy isotope $^{15} ext{NH}_4 ext{Cl}$, separated by CsCl density gradient centrifugation.
- Taylor and colleagues used radioactive thymidine on Vicia faba (faba beans) to prove semi-conservative replication in chromosomes.
- Genetic Code Features:
- 64 codons: 61 code for 20 amino acids; 3 stop codons (UAA, UAG, UGA).
- Unambiguous (one codon codes for one amino acid) and degenerate (some amino acids coded by more than one codon).
- Initiator codon: AUG (codes for Methionine).
- The Lac Operon Components:
- Promoter (p), Operator (o), Regulator gene (i - codes for repressor protein constitutively).
- Structural genes: z (beta-galactosidase), y (permease), a (transacetylase).
- Inducer: Lactose / Allolactose. Negative regulation system under repressor control.
2. Unit V: Human Physiology High-Yield Matrix
Human Physiology spans 7 chapters with high diagnostic and clinical relevance. NTA questions test hormonal regulation, feedback loops, and volume values:
| System / Chapter | Critical NCERT Volume / Value | High-Yield Feedback Mechanism |
|---|---|---|
| Breathing & Gas Exchange | Tidal Volume (500 mL), Vital Capacity (3500–4500 mL), Residual Volume (1100–1200 mL) | Respiratory rhythm center in Medulla; Pneumotaxic center in Pons modulates rate |
| Body Fluids & Circulation | Cardiac Output = $70 ext{ mL} imes 72 = 5040 ext{ mL/min}$; SAN action potential = 70–75/min | Sympathetic nerves increase cardiac output; Parasympathetic (Vagus) decreases heart rate |
| Excretory Products | GFR = 125 mL/min (180 L/day); 99% reabsorbed | RAAS (Renin-Angiotensin-Aldosterone System) increases GFR; ANF decreases blood pressure |
| Locomotion & Movement | 206 bones: 80 Axial, 126 Appendicular; 12 pairs of ribs (7 True, 3 Vertebrochondral, 2 Floating) | Sliding Filament Theory: Calcium binds Troponin C, unmasking Myosin binding sites on Actin |
| Neural Control | Resting potential = -70 mV ($K^+$ permeable); Action potential generated by rapid $Na^+$ influx | Transmission across electrical synapse faster than chemical; neurotransmitters stored in vesicles |
| Chemical Coordination | Peptide hormones (Insulin, Glucagon, Pituitary); Steroid hormones (Cortisol, Testosterone, Estrogen) | Steroids bind intracellular receptors; Peptides generate secondary messengers (cAMP, $IP_3$) |
3. High-Yield Diagram Trap Matrix for NEET 2026
To prevent losing marks to diagram identification questions:
- Replication Fork (NCERT Class 12, Page 106): Continuous synthesis on $3' o 5'$ template strand; discontinuous Okazaki fragments on $5' o 3'$ template strand.
- tRNA Adapter Molecule (NCERT Class 12, Page 114): Cloverleaf 2D structure, inverted L-shaped 3D actual structure. Amino acid binding site at $3'$ end (CCA terminus); anticodon loop at bottom.
- ECG Waves (NCERT Class 11, Page 286):
- P-Wave: Depolarization of Atria.
- QRS Complex: Depolarization of Ventricles (marks start of ventricular systole).
- T-Wave: Repolarization of Ventricles (marks end of systole).
4. Cross-Study Resources & Daily Timetable
To translate NCERT line-by-line reading into examination confidence:
- Calculate your projected All India Rank on our NEET Marks vs Rank Estimator.
- Download authentic past 10-year question papers from the Competitive Exam PYQ Archive.
- Explore the complete preparation roadmap on the NEET Exam Hub or examine NEET Chapter Weightage Breakdown.
- Practice computerized timing drills on the Student CBT Mock Test Engine.
Frequently Asked Questions (FAQ)
Q1: Is reading Class 11 & 12 NCERT Biology enough to score 350+ in NEET?
Yes. Over 95% of questions in NEET Biology are direct factual lines or derived concepts from NCERT textbooks. Supplementary reference books should only be consulted to resolve doubts in genetics numericals.
Q2: How many times should an aspirant revise NCERT Biology before NEET 2026?
Top rankers revise Class 11 and Class 12 NCERT Biology at least 6 to 8 times completely. Use active recall question-framing after every page.