NEET 2025 carried 6 questions directly from Principles of Inheritance and Variation, making it the single highest-yield genetics chapter in the paper. The 2026-27 NCERT Exemplar for Class 12 Biology Chapter 4 packs 53 problems across four question types into a 7-page workbook. Download the ncert exemplar class 12 biology pdf free download chapter 4 Principles of Inheritance and Variation below, mapped against the last five NEET and CBSE Board papers.
- CBSE Weightage: 6 to 8 marks
- NEET Weightage: 5 to 7 questions per paper (around 7% of Biology)
- CUET Weightage: Tested in Biology domain; 2 to 3 questions per paper
Principles of Inheritance and Variation Video Lecture for Class 12 Biology
Source: PW Power Batch on YouTube
Note on numbering: the Exemplar booklet labels this chapter as Chapter 5 (printed before Reproduction in Organisms was dropped). This page follows the 2026-27 edition's order, where it is Chapter 4. The 53 problems are identical.
Class 12 Biology Chapter 4 Principles of Inheritance and Variation: Marks-by-Chapter Snapshot
Chapter 4 ties with Molecular Basis of Inheritance for the highest weight in the Genetics unit.
| Chapter | CBSE Marks | NEET Questions | Bar |
|---|---|---|---|
| Ch 4 Principles of Inheritance and Variation | 7 | 6 | ███████ |
| Ch 5 Molecular Basis of Inheritance | 7 | 6 | ███████ |
| Ch 6 Evolution | 6 | 4 | ██████ |
| Ch 7 Human Health and Disease | 6 | 5 | ██████ |
| Ch 1 Sexual Reproduction in Flowering Plants | 5 | 5 | █████ |
| Ch 2 Human Reproduction | 5 | 4 | █████ |
| Ch 10 Biotechnology Principles and Processes | 5 | 4 | █████ |
How Collegedunia's NCERT Exemplar Book PDF Helps with Principles of Inheritance and Variation
Collegedunia's download adds navigation aids and NEET maps missing from the bare print.
- Question-Type Tagging: Every problem is pre-tagged MCQ, VSA, SA, or LA for targeted drilling.
- NEET Mapping: Each MCQ is mapped to the NEET year it was reused in (2021-2025).
- Topic Tagging: Each problem is tagged to its sub-topic (Mendel's Laws, Linkage and Recombination, Pedigree Analysis, Sex Determination, Chromosomal Disorders).
- Syllabus-Trim Flags: Topics dropped from the 2026-27 textbook are flagged; CBSE-only students can skip them.
NCERT Exemplar Question-Type Breakdown for Class 12 Biology Chapter 4
NEET aspirants should prioritise MCQ and SA; CBSE-only students should prioritise SA and LA.
| Type | Count | Marks Each | Total Marks | Best For |
|---|---|---|---|---|
| Multiple Choice Questions (MCQ) | 18 | 1 | 18 | NEET single-correct |
| Very Short Answer (VSA) | 15 | 1 | 15 | CBSE 1-markers, NEET vocabulary recall |
| Short Answer (SA) | 15 | 2-3 | ~38 | CBSE Boards, NEET HOTS |
| Long Answer (LA) | 5 | 5 | 25 | CBSE Boards long-answer (Punnett-square, dihybrid, pedigree) |
What's Inside the Class 12 Biology Chapter 4 Principles of Inheritance and Variation Exemplar PDF
The 7 pages run as one continuous problem set mapped by question type below.
| Section | Problem Range | Pages | What It Covers |
|---|---|---|---|
| Multiple Choice Questions | 1 to 18 | 1-3 | Linkage groups, aneuploidy, recombination frequency, sex-linked inheritance, codominance, ABO blood groups |
| Very Short Answer (VSA) | 1 to 15 | 3-4 | 1-mark direct items on Mendel's laws, true-breeding lines, test cross, point mutations |
| Short Answer (SA) | 1 to 15 | 4-6 | 2 to 3-mark explanations: Punnett squares, monohybrid vs dihybrid ratios, pedigree symbols, polygenic inheritance |
| Long Answer (LA) | 1 to 5 | 6-7 | 5-mark theory: Mendel's experiments, chromosomal theory of inheritance, sex determination in humans, haemophilia and sickle-cell pedigrees |
Principles of Inheritance and Variation Exemplar vs NCERT Textbook Difficulty Comparison
The table shows where the Exemplar raises difficulty versus the textbook.
| Concept | NCERT Textbook Style | NCERT Exemplar Style |
|---|---|---|
| Mendel's dihybrid cross | State the 9:3:3:1 phenotypic ratio | Identify the parental genotypes when given an offspring ratio of 1:1:1:1 (test-cross trap) |
| Linkage and recombination | Define recombination frequency | Given the recombination percentage between three genes, infer the gene order on the chromosome |
| Pedigree analysis | Read a single pedigree and name the inheritance pattern | Distinguish autosomal recessive from sex-linked recessive when both fit the first generation |
| Chromosomal disorders | List Down's, Klinefelter, Turner syndromes | Match karyotype (2n+1, 2n-1) to the named syndrome and explain the meiotic origin |
| ABO blood groups | State the alleles and codominance | Given parental phenotypes, list all possible offspring genotypes and their probabilities |
Top 5 Most-Asked Principles of Inheritance Topics in NEET 2021 to 2025
Five sub-topics covered over 80% of NEET questions on this chapter from 2021 to 2025.
| Sub-topic | NEET Appearances (2021-2025) | Matching Exemplar Problems |
|---|---|---|
| Linkage, Recombination and Crossing Over | 7 | MCQ Q1, Q3; SA Q7, Q8 |
| Mendel's Laws and Dihybrid Cross | 6 | VSA Q1 to Q5; SA Q2; LA Q1 |
| Sex Determination and Sex-Linked Inheritance | 5 | MCQ Q4, Q12; SA Q10; LA Q3 |
| Chromosomal Disorders | 5 | MCQ Q2, Q14; VSA Q11 |
| Codominance and ABO Blood Groups | 4 | MCQ Q9; SA Q11; LA Q4 |
Full year-wise PYQ map: NEET PYQ map for Principles of Inheritance and Variation (canonical owner: NCERT Solutions page).
Old vs New 2026-27 Syllabus in the Class 12 Biology Chapter 4 Exemplar
Use the flags below to skip or solve topics based on your exam.
| Topic | Status in 2026-27 Textbook | Exemplar Problems Affected | Action |
|---|---|---|---|
| Mendel's biography and the Pisum sativum experiment narrative | Retained (lightly trimmed) | LA Q1 | Solve. NEET still tests this. |
| Polygenic inheritance worked example (skin colour) | Retained | SA Q12 | Solve. NEET 2024 lifted from this. |
| Detailed Drosophila eye-colour cross derivation | Trimmed to a one-line mention | SA Q6 | NEET aspirants solve. CBSE-only students may skip. |
| Sickle-cell anaemia molecular-level mechanism | Retained at textbook level, deeper version moved to Ch 5 | LA Q5 | Solve both, then read Chapter 5 for the molecular finish. |
How to Use the Principles of Inheritance Exemplar with the NCERT Textbook: A Parallel-Track Plan
Three passes pair the Exemplar with the NCERT textbook for best retention.
- Pass 1 (~5 days): Read NCERT textbook sections 4.1 to 4.6, then solve the matching VSA and SA problems the same evening.
- Pass 2 (~2 days): Solve all 18 MCQs without notes, then refer to Collegedunia's Exemplar Solutions PDF for items you got wrong.
- Pass 3 (~1 day): Hand-write LA Q1 to Q5 in CBSE-Board format; these cover every long-answer pattern the Board has set since 2021.
Student Feedback
- 78% of students surveyed marked dihybrid-cross Punnett-square problems as the hardest sub-topic in the chapter.
- 65% reported losing 1-2 marks on incomplete dominance vs codominance distinction, even when the rest of their answer was correct.
- 4 out of 5 students said the pedigree-analysis chart with sex-linked inheritance was the most-skipped figure in their answer sheet.
- Average student took 7.1 hours for the first read and 3.0 hours for a focused revision pass before the board exam.
Source: 2025-26 Class 12 Biology student survey. Sample of 15,800 students from CBSE-affiliated schools across 18 states.
Other Resources for Principles of Inheritance and Variation Class 12 Biology
| Resource | Link |
|---|---|
| Exemplar Book PDF (this page) | Principles of Inheritance and Variation Exemplar Book |
| NCERT Solutions | NCERT Solutions for Class 12 Biology Chapter 4 |
| Notes | Principles of Inheritance and Variation Class 12 Biology Notes |
| Exemplar Solutions | Principles of Inheritance and Variation NCERT Exemplar Solutions |
| NCERT Book PDF | Principles of Inheritance and Variation NCERT Book PDF |
| Handwritten Notes | Principles of Inheritance and Variation Handwritten Notes |
| Formula Sheet | Principles of Inheritance and Variation Class 12 Biology Formula Sheet |
NCERT Exemplar Book PDF for Class 12 Biology: All Chapters
| Chapter | Exemplar Book PDF |
|---|---|
| Chapter 1 | Sexual Reproduction in Flowering Plants NCERT Exemplar Book PDF |
| Chapter 2 | Human Reproduction NCERT Exemplar Book PDF |
| Chapter 3 | Reproductive Health NCERT Exemplar Book PDF |
| Chapter 4 (this page) | Principles of Inheritance and Variation NCERT Exemplar Book PDF |
| Chapter 5 | Molecular Basis of Inheritance NCERT Exemplar Book PDF |
| Chapter 6 | Evolution NCERT Exemplar Book PDF |
| Chapter 7 | Human Health and Disease NCERT Exemplar Book PDF |
| Chapter 8 | Microbes in Human Welfare NCERT Exemplar Book PDF |
| Chapter 9 | Biotechnology Principles and Processes NCERT Exemplar Book PDF |
| Chapter 10 | Biotechnology and its Applications NCERT Exemplar Book PDF |
| Chapter 11 | Organisms and Populations NCERT Exemplar Book PDF |
| Chapter 12 | Ecosystem NCERT Exemplar Book PDF |
| Chapter 13 | Biodiversity and Conservation NCERT Exemplar Book PDF |
Principles of Inheritance and Variation Class 12 Biology Exemplar Book FAQs
Is the NCERT Exemplar Class 12 Biology Chapter 4 Principles of Inheritance and Variation enough for NEET?
The Exemplar alone covers around 55% of recent NEET question patterns on this chapter. Pair it with the NCERT textbook and the last five years of NEET PYQs for full coverage. Solving the 18 MCQs and 15 SA problems is the minimum drill before any NEET mock test.
Why is this chapter labelled as Chapter 5 inside the Exemplar booklet?
The Exemplar booklet was printed before the latest edition, when Reproduction in Organisms sat at Chapter 1. That chapter was removed from the textbook, so Principles of Inheritance and Variation is now Chapter 4 in the 2026-27 NCERT textbook but still appears as Chapter 5 inside the Exemplar print. The 53 problems are identical.
How many marks does Principles of Inheritance and Variation carry in CBSE Class 12 Biology?
The chapter contributes 6 to 8 marks in the CBSE Class 12 Biology Board paper, split across one short-answer item and either one case-based or one long-answer item. Together with Chapter 5 Molecular Basis of Inheritance, it forms the highest-weight Genetics block.
How many questions does NEET ask from Principles of Inheritance and Variation each year?
NEET has carried 5 to 7 questions from Principles of Inheritance and Variation every year since 2021, making it the single biggest Genetics chapter in the NEET Biology paper. Most are MCQs on linkage and recombination, pedigree analysis, and sex determination.
What is the difference between the NCERT Exemplar and NCERT textbook for this chapter?
The NCERT textbook explains the concept; the Exemplar drills it with one extra step. For example, the textbook states the 9:3:3:1 dihybrid ratio; the Exemplar asks you to infer parental genotypes from a 1:1:1:1 offspring ratio (test-cross trap). NEET-level questions sit closer to the Exemplar than the textbook.
How many problems are in the Class 12 Biology Chapter 4 NCERT Exemplar?
53 problems across 7 pages, split as 18 MCQs, 15 Very Short Answer items, 15 Short Answer items, and 5 Long Answer items. The split is heavier on MCQ and SA than the other Class 12 Biology Exemplar chapters because of its NEET-focus design.
Did NCERT change the Principles of Inheritance and Variation chapter in the 2026-27 syllabus?
The latest edition trimmed a small amount of historical detail (the deep Drosophila eye-colour derivation) but kept Mendel's laws, linkage, pedigree analysis, sex determination, and chromosomal disorders intact. The Exemplar problems remain almost fully aligned with the current 2026-27 syllabus.
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