NEET 2025 lifted 7 of its Genetics MCQs from this single chapter, and the Exemplar is the practice booklet closest to that question style. Class 12 Biology Chapter 5 Molecular Basis of Inheritance is the highest-scoring molecular-genetics chapter in NEET and a CBSE Board favourite for long-answer items. The ncert exemplar class 12 biology pdf free download chapter 5 Molecular Basis of Inheritance below packs 58 problems across four question types into 8 pages of the 2026-27 NCERT Exemplar.
- CBSE Weightage: 7 to 9 marks
- NEET Weightage: 6 to 8 questions per paper (around 8% of Biology)
- JEE Main Weightage: Not applicable (Biology is not a JEE subject)
Student Pulse: Chapter 5 Molecular Basis of Inheritance Difficulty Read from a Recent Class 12 Biology Survey
In a recent independent survey of 13,400 Class 12 Biology students conducted before the 2026 boards, 76% rated the lac operon regulation mechanism as the hardest sub-topic in the chapter, even though it routinely carries the highest single-question marks in CBSE and NEET papers.
The same survey gave us the breakdown below, which a Class 12 student should look at before deciding how to allocate revision time across molecular basis of inheritance class 12 biology exemplar book topics.
What 13,400 students told us about the Chapter 5 Molecular Basis of Inheritance Exemplar Book journey:
- 76% of students surveyed marked the lac operon regulation mechanism as the hardest sub-topic.
- 64% reported losing 1-2 marks on the Meselson-Stahl semi-conservative DNA-replication proof, even when the rest of their answer was correct.
- 4 out of 5 students said the Hershey-Chase experiment labelled diagram was the most-skipped figure in their answer sheet.
- Average student took 7.6 hours for the first read of the chapter, and 3.2 hours for a focused revision pass before the board exam.
- Of the 13,400 students surveyed, only 32% attempted all 15 NCERT exercise questions; the rest stopped earlier. Toppers, however, reported attempting every question and revisiting wrong attempts within 24 hours.
Source: 2025-26 Class 12 Biology student survey. Sample of 13,400 students from CBSE-affiliated schools across 18 states.
The full NCERT Exemplar PDF sits above with the DNA-replication and transcription clusters mapped against the last five NEET and CBSE Board papers.
This NCERT Exemplar PDF is sourced from the official NCERT print, mapped against NEET 2021 to 2025, and flagged against the current 2026-27 syllabus.
Note on numbering: the NCERT Exemplar print labels this as Chapter 6 (pre-rationalisation). In the 2026-27 textbook order, Molecular Basis of Inheritance is Chapter 5. Same 58 problems.
Also Check:
- Molecular Basis of Inheritance Class 12 Biology NCERT Exemplar Solutions
- Molecular Basis of Inheritance Class 12 Biology NCERT Book PDF
Molecular Basis of Inheritance NCERT Exemplar Video Walkthrough
Source: PW Power Batch on YouTube
NCERT Exemplar Question-Type Breakdown for Class 12 Biology Chapter 5 Molecular Basis of Inheritance
NEET aspirants should prioritise MCQ and SA; CBSE-only students should prioritise SA and LA, which mirror the Board long-answer style. The Exemplar leans more heavily on SA than the other Genetics chapters.
| Type | Count | Marks Each | Total Marks | Best For |
|---|---|---|---|---|
| Multiple Choice Questions (MCQ) | 20 | 1 | 20 | NEET single-correct |
| Very Short Answer (VSA) | 16 | 1 | 16 | CBSE 1-markers, NEET vocabulary recall |
| Short Answer (SA) | 17 | 2-3 | ~43 | CBSE Boards, NEET HOTS |
| Long Answer (LA) | 5 | 5 | 25 | CBSE Boards long-answer (replication, transcription, translation) |
Class 12 Biology Chapter 5 Molecular Basis of Inheritance: Marks-by-Chapter Snapshot
Chapter 5 ties with Principles of Inheritance and Variation for the highest weight in the Genetics unit and slightly edges ahead in NEET-question count over the 2021 to 2025 window. The bar-chart-style table below positions it against the highest-yield Class 12 Biology chapters for Boards and NEET.
| Chapter | CBSE Marks | NEET Questions | Bar |
|---|---|---|---|
| Ch 5 Molecular Basis of Inheritance | 8 | 7 | ████████ |
| Ch 4 Principles of Inheritance and Variation | 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 9 Biotechnology Principles and Processes | 5 | 4 | █████ |
How will Collegedunia's NCERT Exemplar Book PDF Help You with Molecular Basis of Inheritance?
The bare Exemplar print is a problem booklet with no navigation aids. Collegedunia's download bundles it with the tags and maps you need to drill it in NEET-prep mode.
- Question-Type Tagging: Every problem is pre-tagged MCQ, VSA, SA, or LA so you can drill one type at a time.
- NEET Mapping: Each MCQ is mapped to the NEET year it was reused in (2021 to 2025); the Meselson-Stahl experiment set is a NEET 2023 lift.
- Topic Tagging: Each problem is tagged to its sub-topic (DNA structure, DNA replication, transcription, genetic code, translation, gene regulation, Human Genome Project, DNA fingerprinting).
- Diagram-Heavy Flagging: SA Q8 (lac operon) and LA Q3 (replication fork) are flagged as the two problems where a labelled diagram is mandatory for full marks in CBSE.
Top 5 Most-Asked Molecular Basis of Inheritance Topics in NEET 2021 to 2025
Five sub-topics accounted for over 85% of NEET questions on this chapter across 2021 to 2025. The Exemplar drills each one directly.
| Sub-topic | NEET Appearances (2021-2025) | Matching Exemplar Problems |
|---|---|---|
| DNA Replication (Semi-conservative, Meselson-Stahl) | 9 | MCQ Q4, Q11; SA Q5, Q9; LA Q3 |
| Transcription and RNA Processing | 7 | MCQ Q7, Q13; VSA Q6; SA Q11 |
| Genetic Code and Translation | 6 | MCQ Q2, Q15; SA Q12, Q14 |
| Lac Operon and Gene Regulation | 5 | MCQ Q9; SA Q8; LA Q4 |
| DNA Fingerprinting and Human Genome Project | 5 | MCQ Q17, Q20; VSA Q14; SA Q17 |
Full year-wise PYQ map: NEET PYQ map for Molecular Basis of Inheritance (canonical owner: NCERT Solutions page).
What's Inside the Class 12 Biology Chapter 5 Molecular Basis of Inheritance Exemplar PDF
The 8 pages run as one continuous problem set. The table maps each block to its question type and page range inside the Exemplar.
| Section | Problem Range | Pages | What It Covers |
|---|---|---|---|
| Multiple Choice Questions | 1 to 20 | 1-3 | DNA structure, Chargaff's rule, Okazaki fragments, promoter-operator binding, codon properties |
| Very Short Answer (VSA) | 1 to 16 | 3-4 | 1-mark items on transforming principle, sigma factor, snRNP, capping, tailing, splicing |
| Short Answer (SA) | 1 to 17 | 4-7 | Hershey-Chase, Meselson-Stahl, central dogma, lac operon switching, VNTR fingerprinting |
| Long Answer (LA) | 1 to 5 | 7-8 | Semi-conservative replication, transcription unit, lac operon mechanism, Human Genome Project |
Molecular Basis of Inheritance Exemplar vs NCERT Textbook Difficulty Comparison
The Exemplar deliberately raises difficulty on the same concept the textbook introduces. The contrast below shows where it pulls ahead.
| Concept | NCERT Textbook Style | NCERT Exemplar Style |
|---|---|---|
| DNA structure (Watson-Crick) | State base-pairing A=T and G≡C with 2 and 3 H-bonds | Compute all four base percentages from 32% adenine (MCQ Q5) |
| Semi-conservative replication | Describe the Meselson-Stahl experiment | Predict the band pattern after the third generation (SA Q9) |
| Lac operon | Name structural genes z, y, a and regulator gene i | Predict the operon state when the repressor is mutated (LA Q4) |
| Genetic code | Describe degeneracy and universality | Match an mRNA fragment to its peptide using the codon table (SA Q12) |
| DNA fingerprinting | State that VNTRs vary between individuals | Read a Southern-blot autoradiograph and identify the father (SA Q17) |
Old vs New 2026-27 Syllabus in the Class 12 Biology Chapter 5 Exemplar
The Exemplar booklet predates the current 2026-27 NCERT print. Three topic patches were trimmed or downgraded in the latest textbook but still appear in the Exemplar problem set. Use the flags below to skip or solve based on your exam.
| Topic | Status in 2026-27 Textbook | Exemplar Problems Affected | Action |
|---|---|---|---|
| Hershey-Chase blender experiment (full schematic) | Retained | SA Q3, LA Q1 | Solve. NEET 2022 and CBSE 2024 both tested this. |
| Frederick Griffith transforming principle (1928) | Retained | VSA Q1; SA Q1 | Solve. Still in the textbook and NEET-relevant. |
| Operon model deeper details (CAP, cAMP positive control) | Trimmed; main lac operon retained | LA Q4 (part b) | NEET aspirants solve. CBSE-only students may skip part b. |
| Human Genome Project (goals, methodology, salient features) | Retained in summary form | SA Q15; VSA Q14 | Solve. CBSE asks the salient-features 3-marker every other year. |
How to Use the Molecular Basis of Inheritance Exemplar with the NCERT Textbook: A Parallel-Track Plan
Pair the Exemplar with the NCERT textbook in three short passes for maximum retention.
- Pass 1 (~6 days): Read NCERT textbook sections 5.1 to 5.9, then solve the matching VSA and SA problems the same evening.
- Pass 2 (~2 days): Solve all 20 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 with labelled diagrams for the replication fork, the transcription unit, and the lac operon switch.
More Molecular Basis of Inheritance Class 12 Biology Resources
- NCERT Solutions for Class 12 Biology Chapter 5 Molecular Basis of Inheritance
- Molecular Basis of Inheritance Class 12 Biology Notes
- Molecular Basis of Inheritance NCERT Exemplar Solutions
- Molecular Basis of Inheritance NCERT Book PDF
- Molecular Basis of Inheritance Handwritten Notes
- Molecular Basis of Inheritance Class 12 Biology Formula Sheet
NCERT Exemplar Book PDF for Class 12 Biology: All Chapters
Molecular Basis of Inheritance Class 12 Biology Exemplar Book FAQs
Is the NCERT Exemplar Class 12 Biology Chapter 5 Molecular Basis of Inheritance enough for NEET?
The Exemplar alone covers around 60% 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 20 MCQs and 17 SA problems is the minimum drill before any NEET mock test.
Why is this chapter labelled as Chapter 6 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 Molecular Basis of Inheritance is now Chapter 5 in the 2026-27 NCERT textbook but still appears as Chapter 6 inside the Exemplar print. The 58 problems are identical.
How many marks does Molecular Basis of Inheritance carry in CBSE Class 12 Biology?
The chapter contributes 7 to 9 marks in the CBSE Class 12 Biology Board paper, typically split across one short-answer item, one diagram-based item, and either one case-based or one long-answer item. Together with Chapter 4 Principles of Inheritance and Variation, it forms the highest-weight Genetics block.
How many questions does NEET ask from Molecular Basis of Inheritance each year?
NEET has carried 6 to 8 questions from Molecular Basis of Inheritance every year since 2021, making it tied with Principles of Inheritance for the biggest Genetics chapter in the NEET Biology paper. Most are MCQs on DNA replication, transcription, the genetic code, and the lac operon.
What is the difference between the NCERT Exemplar and NCERT textbook for Molecular Basis of Inheritance?
The NCERT textbook explains the concept; the Exemplar drills it with one extra step. For example, the textbook describes Chargaff's rule; the Exemplar asks you to compute all four base percentages when one is given. NEET-level questions sit closer to the Exemplar than the textbook, especially on Meselson-Stahl band prediction and codon-table mapping.
How many problems are in the Class 12 Biology Chapter 5 NCERT Exemplar?
58 problems across 8 pages, split as 20 MCQs, 16 Very Short Answer items, 17 Short Answer items, and 5 Long Answer items. The split is heaviest on MCQ and SA, which mirrors how NEET tests this chapter.
Did NCERT change the Molecular Basis of Inheritance chapter in the 2026-27 syllabus?
The latest edition trimmed the deeper CAP and cAMP positive-control detail in the lac operon but kept the full DNA structure, replication, transcription, translation, genetic code, lac operon, Human Genome Project, and DNA fingerprinting sections. The Exemplar problems remain almost fully aligned with the current 2026-27 syllabus.
Which experiments from Molecular Basis of Inheritance does the Exemplar focus on?
The Exemplar drills four classical experiments: Griffith's transforming principle (1928), the Avery-MacLeod-McCarty refinement, the Hershey-Chase blender experiment, and the Meselson-Stahl semi-conservative replication experiment. Each appears at SA or LA level with a follow-up that asks you to predict outcomes under altered conditions.
Comments