CBSE · Class 10 · Science · Chapter 8
Heredity — Class 10 Science (CBSE) explained
- Board exam 2026-27
- 3 lessons
- 26 scenes
- About 20 min
- Updated
Quick answer
Heredity is Chapter 8 of CBSE Class 10 Science. It covers reproduction and variation, variation in asexual reproduction, the F₂ evidence, dominant and recessive traits, chromosomes and inheritance and human sex chromosomes. AI Lessons teaches it in 3 narrated lessons (about 20 minutes) with an AI tutor and board-pattern practice.
What you’ll learn
Lesson 1: Variation and the First Rules of Inheritance
6 min- Similar, but Subtly Different
- Follow Diversity Through Generations
- Small Differences During Asexual Reproduction
- When a Variation Helps Survival
- Inherited Traits: Observe Earlobes
- A Trait Can Be Influenced by Both Parents
- Mendel Combines Observation and CountingNot assessed
- The First Generation Is All Tall
Lesson 2: Reading Mendel’s Crosses
6 min- Short Plants Reappear in F₂
- Dominant and Recessive Traits
- A Visible Trait Does Not Reveal Every Combination
- Infer Dominance from Flower Colour
- Two Traits Can Be Inherited Independently
- Seed Shape and Colour: Parents to F₁
- Read the F₂ Grid One Cell at a Time
- Count the Four Seed Combinations
Lesson 3: How Genes Work and How Sex Is Determined
8 min- A Gene Provides Information for a Protein
- How a Gene Can Affect Plant Height
- Two Gene Sets in the Plant, One in Each Germ Cell
- Chromosomes Organise Inheritance
- Different Species Use Different Strategies
- Human Sex Chromosomes: X and Y
- Trace the Paternal X or Y
- Explain What the Evidence Shows
- Prepare Your Exercise Strategy
- Recap: Connect Inheritance, Expression and Survival
Key concepts
- Reproduction and variation
- Quite distinct variations are visible among different individuals. Some variation also arises during asexual reproduction.
- Variation in asexual reproduction
- The differences are minor, while the common body design remains.
- The F₂ evidence
- Shortness reappears even though every F₁ plant is tall.
- Dominant and recessive traits
- Dominant describes which trait is expressed when the copies differ. It does not mean the other copy disappears.
- Chromosomes and inheritance
- The mechanism explains Mendel's results and is used by sexually reproducing organisms. Asexually reproducing organisms also follow similar inheritance rules.
- Human sex chromosomes
- Most human chromosomes have a maternal copy and a paternal copy.
Exam focus
- Board exam
- CBSE assesses this chapter in the 2026-27 year-end board examination.
- Syllabus
- Heredity: Heredity; Mendel's contribution- Laws for inheritance of traits: Sex determination: brief introduction.
- Not assessed
- These parts go beyond the 2026-27 syllabus and are taught for understanding only: Mendel Combines Observation and Counting.
- Exam note
- Evolution is formative-only this session and is not part of this textbook chapter.
- Paper pattern
- 80 marks, 3 hours, 39 questions in three sections (A Biology, B Chemistry, C Physics); internal assessment 20. Units: I Chemical Substances 25, II World of Living 25, III Natural Phenomena 12, IV Effects of Current 13, V Natural Resources 5.
- Question style
- About 50% of board questions are competency-focused: case-based, source-based, integrated, data interpretation, situational and application-oriented.
- Practice in the app
- 79 board-pattern questions with marking schemes: 20 multiple choice (1 mark), 11 assertion–reason (1 mark), 17 very short answer (2 marks), 17 short answer (3 marks), 3 long answer (5 marks) and 11 case-based (4 marks).
Sample questions with marking points
Board-pattern questions from the AI Lessons practice set for this chapter. The marking points show what an examiner looks for; full model answers are in the app.
Very short answer2 marks
For the cross RR yy x rr YY, write the gamete contributed by each parent and give the gene combination and appearance of the F₁ seeds.
Marking points
- The RR yy parent contributes Ry.0.5
- The rr YY parent contributes rY.0.5
- The F₁ gene combination is Rr Yy.0.5
- The F₁ seeds are round and yellow.0.5
Short answer3 marks
During a heat wave, a student argues that all bacterial variants should survive equally well because they belong to the same species. Evaluate this claim and explain how variation can promote survival.
Marking points
- Rejects equal survival and explains that advantages depend on the nature of variations and environmental conditions.1
- Bacteria able to withstand heat survive better during a heat wave.1
- Variation can promote survival because some individuals possess advantageous differences under the prevailing conditions.1
Long answer5 marks
(a) Explain how an alteration in a gene can result in a short pea plant through its effect on an enzyme and a growth-triggering hormone. (3 marks) (b) Explain how germ cells and chromosomes ensure equal genetic contribution from both parents while maintaining the normal chromosome number. (2 marks)
Marking points
- A gene is a section of DNA providing information for one protein.1
- An alteration in the gene for the hormone-production enzyme may make the enzyme less efficient.1
- Lower enzyme efficiency reduces growth-triggering hormone production, resulting in a short plant.1
- Each germ cell carries one gene set and takes one chromosome from each pair.1
- Combination of germ cells restores the normal chromosome number, with one chromosome of each pair contributed by each parent.1
Frequently asked questions
What does Heredity cover in Class 10 Science?
It covers reproduction and variation, variation in asexual reproduction, the F₂ evidence, dominant and recessive traits, chromosomes and inheritance and human sex chromosomes. AI Lessons teaches it in 3 lessons: Variation and the First Rules of Inheritance, Reading Mendel’s Crosses and How Genes Work and How Sex Is Determined.
Is Heredity in the CBSE Class 10 board exam?
Yes. CBSE assesses Heredity in the 2026-27 year-end board examination. 1 short part goes beyond the syllabus and is marked as not assessed.
What is the earlobe?
The earlobe is the lowest part of the ear. In some people, it is closely attached to the side of the head.
What kinds of questions come from Heredity?
Board-pattern questions for this chapter include multiple choice (1 mark), assertion–reason (1 mark), very short answer (2 marks), short answer (3 marks), long answer (5 marks) and case-based (4 marks). AI Lessons has 79 of them for Heredity, each with a marking scheme.
How does AI Lessons teach Heredity?
As 3 narrated, animated lessons (26 scenes, about 20 minutes in all), with an AI tutor that knows the step you are on and board-pattern practice with marking schemes. The full lessons open after sign-in on an AI Lessons account.
Watch the full lesson
Heredity, as a narrated, animated lesson
3 lessons · 26 animated scenes · about 20 minutes, with an AI tutor that knows the step you are on and 79 board-pattern questions with marking schemes.
Lessons open after sign-in. A parent or guardian holds the account and adds each child.