TEACHGYAN • CLASS 10 SCIENCE • NCERT 2026–27
Chapter 8: Heredity
Detailed Notes • Diagrams • Experiments • Competency • Board Practice
📖 Chapter Explanation
Heredity explains how characteristics are transmitted from parents to offspring. The chapter develops genes, chromosomes, dominant and recessive traits and simple inheritance patterns, using Mendelian reasoning to connect observable traits with genetic information.
🧭 Concept Map
🔬 Core Science
A gene is a unit of heredity located at a particular position on a chromosome. In a simple Mendelian cross, allele combinations in offspring can be predicted using a Punnett square.
🖼️ Diagram to Draw
Use a labelled textbook-style diagram with arrows, direction of travel and key parts.
💡 Worked/Applied Example
A gene is a unit of heredity located at a particular position on a chromosome. In a simple Mendelian cross, allele combinations in offspring can be predicted using a Punnett square.
⚠️ Common Errors
A cross between two heterozygous individuals Aa × Aa gives possible genotypes AA, Aa, Aa and aa, giving a 1:2:1 genotype ratio.
🧠 Concept-Based MCQs
- Two parents are heterozygous for a trait represented by A/a. Construct a Punnett square and calculate the probability of an aa offspring.
Answer Key: 1-A, 2-A, 3-C, 4-C.
📊 Case-Based / Competency
Do not say that a dominant trait is necessarily more common or stronger. Dominance describes expression in a particular genetic relationship.
- Identify the scientific concept involved.
- Draw/interpret the required diagram or model.
- Apply the principle step by step.
- Explain and verify the conclusion.
🔎 Extension Case
A dominant allele is represented by: A) usually an uppercase symbol B) only a number C) always a lowercase symbol D) a chromosome|Genes are located on: A) chromosomes B) ribs C) enzymes only D) blood plasma|Aa is: A) homozygous dominant B) homozygous recessive C) heterozygous D) non-genetic|The genotype ratio of Aa × Aa is: A) 3:1 B) 1:1 C) 1:2:1 D) 2:1
🧪 Activity / Observation Corner
Design a safe classroom observation related to this chapter. Record the materials, procedure, observation and inference. Where a practical activity is not suitable, use a labelled diagram or simulation-based observation instead.
🔥 HOTS & Board Challenge
- Explain why the phenomenon occurs rather than only naming it.
- Predict what changes if one variable is altered.
- Find and correct a plausible incorrect explanation.
- Connect the concept with a real-life application.
✍️ Exam Practice
- Define the central concept with an example.
- Answer a diagram-based question.
- Solve a multi-step competency problem.
- Explain an application or experiment.
- Write a complete 5-mark answer with scientific reasoning.
📄 Practice Worksheet
- 5 concept checks
- 5 application questions
- 3 diagram-based questions
- 2 case-based questions
- 2 HOTS questions
- 1 board-style challenge
🎯 One-Minute Revision
DNA → genes → chromosomes → inherited traits → alleles → dominant/recessive → probability of inheritance
🏆 Mastery Checklist
- ☐ I can explain the concept scientifically.
- ☐ I can draw and label the key diagram.
- ☐ I can apply the concept to a new situation.
- ☐ I can answer competency/case-based questions.
- ☐ I can justify my conclusion.
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Original explanatory study material aligned to the current NCERT/CBSE framework; textbook passages are not reproduced verbatim.