Class 12 Genetics Important Questions CBSE Biology | Exam Guide
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Class 12 Genetics Important Questions (CBSE Biology) – Complete Exam-Oriented Guide
Genetics is one of the highest-scoring units in CBSE Class 12 Biology. Every year, 15–20 marks come directly from genetics, and most questions are repeated in pattern. If you prepare the right questions, you can easily pass and even score above average.
This article covers most important genetics questions, explained in a simple way, so students can understand concepts just by reading.
Weightage of Genetics in CBSE Class 12 Biology
| Unit | Chapters | Marks (Approx.) |
|---|---|---|
| Genetics & Evolution | Principles of Inheritance, Molecular Basis, Evolution | 20 Marks |
Genetics is must-prepare. Skipping it is risky.
Chapters Covered in Genetics
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Principles of Inheritance and Variation
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Molecular Basis of Inheritance
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Evolution (genetics-based questions)
Most Important Genetics Questions – Chapter Wise
Chapter 1: Principles of Inheritance and Variation
Very Important Theory Questions
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State Mendel’s laws of inheritance.
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Explain Law of Segregation with an example.
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Explain Law of Independent Assortment.
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What is a monohybrid cross? Draw a Punnett square.
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What is a dihybrid cross? Mention phenotypic ratio.
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Define genotype and phenotype.
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What is test cross? Why is it performed?
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Explain incomplete dominance with example.
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Describe co-dominance using blood group system.
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What is pleiotropy?
Important Numerical / Diagram-Based Questions
| Topic | Expected Question |
|---|---|
| Mendel Cross | Draw Punnett square |
| Blood Group | Explain ABO inheritance |
| Sex Determination | XX–XY mechanism |
| Pedigree Chart | Identify inheritance pattern |
Chapter 2: Molecular Basis of Inheritance
Most Repeated Board Questions
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Describe structure of DNA.
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Explain DNA replication.
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What is central dogma of molecular biology?
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Explain transcription in detail.
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Describe translation process.
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What are codons? Explain genetic code.
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What is lac operon? Draw diagram.
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Differentiate between DNA and RNA.
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Explain gene expression regulation.
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What are mutations? Types of mutations.
Important Diagrams to Practice
| Diagram | Marks |
|---|---|
| DNA structure | 3–5 |
| Replication fork | 3 |
| Lac operon | 5 |
| Transcription process | 3 |
Diagrams carry easy marks if labelled neatly.
Chapter 3: Evolution (Genetics-Linked Questions)
High-Scoring Questions
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What is evolution?
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Explain Hardy-Weinberg principle.
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What are evidences of evolution?
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Explain adaptive radiation.
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What is genetic drift?
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Define speciation.
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What is natural selection?
Genetics – One Day Revision Table
| Time | What to Revise |
|---|---|
| Morning | Mendel crosses & ratios |
| Afternoon | DNA, transcription, translation |
| Evening | Lac operon + diagrams |
| Night | Evolution theory |
How to Write Genetics Answers in Exam
✔ Use NCERT terms only
✔ Write answers in points
✔ Draw clean diagrams
✔ Mention ratios clearly
✔ Avoid unnecessary stories
CBSE checks clarity, not long answers.
Common Mistakes Students Make
- Forgetting Mendel ratios
- Confusing transcription & translation
- Skipping diagrams
- Writing outside NCERT
Avoid these and marks are guaranteed.
Final Advice for CBSE Biology Students
Genetics looks difficult, but once concepts are clear, it becomes one of the easiest scoring units. Focus on important questions, diagrams, and ratios.
- Read NCERT line by line
- Practice diagrams
- Revise smartly
You can easily pass and score well.
FAQs (Frequently Asked Questions)
Yes, it is one of the most repeated 5-mark questions.
No. Evolution is linked with genetics and scoring.
Not compulsory, but strongly recommended for full marks.
Around 20 marks every year.
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