CBSE Class 10 Science Chapter 8 Heredity Important Questions 2027
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27 questions from Heredity appeared in 7 of the 7 CBSE papers we analysed (2022–2026) — here are the topics that matter, the questions that repeat, and every previous-year question from this chapter.
Key facts
- World of Living unit — 25 marks in the official syllabus
- Asked in 7 of 7 analysed papers (2022–2026)
- About 3.9 questions per paper (OR alternatives counted separately)
- 6 question patterns repeated across papers
Important topics in Heredity
| # | Topic | Asked in | Importance |
|---|---|---|---|
| 1 | Mendel's monohybrid cross and laws of inheritance | Board 2022Board 2023Board 2024Board 2025Board 2026Sample 2025Sample 2026 | ★★★☆☆ |
| 2 | Dominant/recessive traits, F1 and F2 ratios | Board 2022Board 2023Board 2024Board 2025Board 2026Sample 2026 | ★★☆☆☆ |
| 3 | Sex determination in humans | Board 2022Board 2023Board 2024Sample 2025 | ★☆☆☆☆ |
Repeated questions from Heredity
1. Dihybrid cross F1/F2 combinations and ratio
4×Board 2023Board 2024Board 2025Board 20261/2 marks
Two pea plants, one with round green seeds (RRyy) and another with wrinkled yellow (rrYY) seeds were crossed with each other which produced F1 progeny that have only round yellow (RrYy) seeds. When F1 plants are self-pollinated, the F2 progeny will have which new combination of characters, as compared to the parents: (i) Round, yellow (ii) Round, green (iii) Wrinkled, yellow (iv) Wrinkled, green. Correct options are: (A) (i) and (ii) (B) (i) and (iv) (C) (ii) and (iv) (D) (i) and (iii)
2. Construct a monohybrid cross and show F1/F2 ratios
3×Board 2023Board 2026Sample 20252/3 marks
Study the given table and answer the following questions: [Parents: A pea plant with red flowers was crossed with a pea plant with white flowers. | F1: 30 seeds were sown and all bore plants with red flowers. | F2: 44 seeds were sown, 33 plants bore red flowers and 11 plants bore white flowers.] (a) Depict the information given in the table in the form of a cross. (b) Deduce the F2 phenotypic ratio / F2 ratio showing external look as well as genotypic/genetic makeup, ratio.
3. Environmental (non-genetic) sex determination
2×Board 2022Sample 20251/2 marks
In snails individuals can begin life as male and depending on environmental conditions they can become female as they grow. This is because A. male snails have dominant genetic makeup. B. female snails have dominant genetic makeup. C. expression of sex chromosomes can change in a snail's life time. D. sex is not genetically determined in snails.
4. Correct statements about genes/chromosomes
2×Board 2023Board 20241 marks
Chromosomes: (i) carry hereditary information from parents to the next generation. (ii) are thread like structures located inside the nucleus of an animal cell. (iii) always exist in pairs in human reproductive cells. (iv) are involved in the process of cell division. The correct statements are: (a) (i) and (ii) (b) (iii) and (iv) (c) (i), (ii) and (iv) (d) (i) and (iv)
5. Sex determined by father / at fertilisation
2×Board 2023Board 20241 marks
Consider the following statements: (i) The sex of a child is determined by what it inherits from the mother. (ii) The sex of a child is determined by what it inherits from the father. (iii) The probability of having a male child is more than that of a female child. (iv) The sex of a child is determined at the time of fertilisation when male and female gametes fuse to form a zygote. The correct statements are: (a) (i) and (iii) (b) (ii) and (iv) (c) (iii) and (iv) (d) (i), (iii) and (iv)
6. Differentiate dominant vs recessive traits
2×Board 2023Board 20241 marks
[case context: Mendel's experiments on inheritance in garden pea.] Write one difference between dominant and recessive trait.
Heredity questions by paper
| Paper | Questions | Marks |
|---|---|---|
| Board 2022 | 6 | 10 |
| Board 2023 | 6 | 8 |
| Board 2024 | 6 | 8 |
| Board 2025 | 2 | 2 |
| Sample 2025 | 2 | 4 |
| Board 2026 | 2 | 4 |
| Sample 2026 | 3 | 5 |
Counts include both options of internal-choice (OR) questions.
Previous year questions: Heredity
Board 2026 2 questions
Two pea plants, one with round green seeds (RRyy) and another with wrinkled yellow (rrYY) seeds were crossed with each other which produced F1 progeny that have only round yellow (RrYy) seeds. When F1 plants are self-pollinated, the F2 progeny will have which new combination of characters, as compared to the parents: (i) Round, yellow (ii) Round, green (iii) Wrinkled, yellow (iv) Wrinkled, green. Correct options are: (A) (i) and (ii) (B) (i) and (iv) (C) (ii) and (iv) (D) (i) and (iii)
Study the given table and answer the following questions: [Parents: A pea plant with red flowers was crossed with a pea plant with white flowers. | F1: 30 seeds were sown and all bore plants with red flowers. | F2: 44 seeds were sown, 33 plants bore red flowers and 11 plants bore white flowers.] (a) Depict the information given in the table in the form of a cross. (b) Deduce the F2 phenotypic ratio / F2 ratio showing external look as well as genotypic/genetic makeup, ratio.
Sample 2026 3 questions
In a cross between black furred rabbit (B) and white furred rabbit (b), all offspring were found to have black fur. What can be inferred about the genetic makeup of the parent rabbits? A. BB X bb B. Bb X Bb C. Bb X bb D. bb X bb
Assertion (A): Tallness of a pea plant is controlled by an enzyme. Reason (R): The gene for that enzyme makes proteins which help the plant to be tall. Options: A. Both A and R are true, and R is the correct explanation of A. B. Both A and R are true, and R is not the correct explanation of A. C. A is true but R is false. D. A is false but R is true.
In a genetic experiment, plants with pure round green seeds (RRyy) were crossed with plants with wrinkled yellow seeds (rrYY). (i) Show the gametes formed when F1 was self-pollinated. (ii) A total of 144 seeds were produced which developed into saplings. Show the ratio in which these traits are independently inherited in these 144 sapling.
Board 2025 2 questions
If pea plants with round and green seeds (RRyy) are crossed with pea plants having wrinkled and yellow seeds (rrYY), the seeds developed by the plants of F1 generation will be : (A) 50% round and green (B) 75% wrinkled and green (C) 100% round and yellow (D) 75% wrinkled and yellow
Assertion (A): A human child bears all the basic features of human beings. Reason (R): It looks exactly like its parents, showing very little variations. Select the correct answer: (A) Both A and R are true and R is the correct explanation of A. (B) Both A and R are true, but R is not the correct explanation of A. (C) A is true, but R is false. (D) A is false, but R is true.
Sample 2025 2 questions
In snails individuals can begin life as male and depending on environmental conditions they can become female as they grow. This is because A. male snails have dominant genetic makeup. B. female snails have dominant genetic makeup. C. expression of sex chromosomes can change in a snail's life time. D. sex is not genetically determined in snails.
A. In a family of four individuals, the father possessed long ears and the mother possessed short ears. If the parents had pure dominant and recessive traits respectively, then calculate the ratio of genetic makeup of F2 generation. Show a suitable cross. (2) B. If father had short ears and the mother had long ears, explain what effect it will have on the ratio of genetic makeup in F2 generation. (1)
Board 2024 6 questions
Consider the following statements: (i) The sex of a child is determined by what it inherits from the mother. (ii) The sex of a child is determined by what it inherits from the father. (iii) The probability of having a male child is more than that of a female child. (iv) The sex of a child is determined at the time of fertilisation when male and female gametes fuse to form a zygote. The correct statements are: (a) (i) and (iii) (b) (ii) and (iv) (c) (iii) and (iv) (d) (i), (iii) and (iv)
Chromosomes: (i) carry hereditary information from parents to the next generation. (ii) are thread like structures located inside the nucleus of an animal cell. (iii) always exist in pairs in human reproductive cells. (iv) are involved in the process of cell division. The correct statements are: (a) (i) and (ii) (b) (iii) and (iv) (c) (i), (ii) and (iv) (d) (i) and (iv)
[case context: Mendel worked out the rules of heredity on garden pea using visible contrasting characters, making crosses with one or two pairs of contrasting characters.] When Mendel crossed pea plants with pure tall and pure short characteristics to produce F1 progeny, which two observations were made by him in F1 plants?
[case context: Mendel's experiments on inheritance in garden pea.] Write one difference between dominant and recessive trait.
[case context: Mendel's experiments on inheritance in garden pea.] In a cross with two pairs of contrasting characters RRYY x rryy (Round Yellow) (Wrinkled Green), Mendel observed 4 types of combinations in F2 generation. By which method did he obtain F2 generation? Write the ratio of the parental combinations obtained and what conclusions were drawn from this experiment.
[case context: Mendel's experiments on inheritance in garden pea.] Justify the statement: "It is possible that a trait is inherited but may not be expressed."
Board 2023 6 questions
The statement that correctly describes the characteristic(s) of a gene is: (a) In individuals of a given species, a specific gene is located on a particular chromosome. (b) A gene is not the information source for making proteins in the cell. (c) Each chromosome has only one gene located all along its length. (d) All the inherited traits in human beings are not controlled by genes.
Assertion (A): Genes inherited from the parents decide the sex of a child. Reason (R): X chromosome in a male child is inherited from his father. Options: (a) Both (A) and (R) are true and (R) is the correct explanation of (A). (b) Both (A) and (R) are true, but (R) is not the correct explanation of (A). (c) (A) is true, but (R) is false. (d) (A) is false, but (R) is true.
[Case context: To trace inheritance of traits Mendel crossed pea plants with contrasting characters; crossing round-yellow seed plants with wrinkled-green seed plants gave no wrinkled-green seeds in F1, and self-pollinating F1 gave F2 with different combinations of seed shape and colour.] Write any two pairs of contrasting characteristics of pea plant used by Mendel other than those mentioned above.
[Case context: Mendel's pea-plant cross experiment tracing inheritance of traits.] Differentiate between dominant and recessive traits.
[Case context: dihybrid cross round-yellow x wrinkled-green pea plants with new combinations appearing in F2.] State the ratio of the combinations observed in the seeds of F2 generation (in the above case). What do you interpret from this result?
[Case context: monohybrid cross - internal choice for sub-part (c).] Given below is a cross between a pure violet flowered pea plant (V) and a pure white flowered pea plant (v). Diagrammatically explain what type of progeny is obtained in F1 generation and F2 generation: Pure violet flowered plant (VV) x Pure white flowered plant (vv).
Board 2022 6 questions
[case context] Sex-determination in humans: humans have 46 (23 pairs) chromosomes; 44 (22 pairs) control body characters and 2 (one pair) are sex chromosomes of two types - X chromosome and Y chromosome; at fertilisation the type of male gamete that fuses with the female gamete decides the sex of the newborn. Why is a pair of sex chromosomes in human beings called a mismatched pair in terms of type and size?
[case context] Sex-determination in humans (46 chromosomes: 44 autosomes + 2 sex chromosomes X and Y; sex of newborn decided by which male gamete fuses with the female gamete). Out of male or female, which of them has a perfect pair of sex chromosomes? In case of a perfect pair, will the gametes produced be of the same kind or of a different kind?
What is variation? List two main reasons that may lead to variation in a population.
(i) In a cross between violet flowered plants and white flowered plants, state the characteristics of the plants obtained in the F1 progeny. (ii) If the plants of F1 progeny are self-pollinated, then what would be observed in the plants of F2 progeny? (iii) If 100 plants are produced in F2 progeny, then how many plants will show the recessive trait?
[case context] Sex-determination in humans (46 chromosomes: 44 autosomes + 2 sex chromosomes X and Y; sex of newborn decided by which male gamete fuses with the female gamete). Write the names of two organisms whose sex determination is not done on a genetic basis. Explain the process of their sex determination.
[case context] Sex-determination in humans (46 chromosomes: 44 autosomes + 2 sex chromosomes X and Y; sex of newborn decided by which male gamete fuses with the female gamete). With the help of a flow chart only, show how sex determination in human beings takes place genetically.
Frequently asked questions
What are the most important topics in CBSE Class 10 Science Chapter 8 Heredity?
By how often and how recently they were asked: Mendel's monohybrid cross and laws of inheritance; Dominant/recessive traits, F1 and F2 ratios; Sex determination in humans.
How many marks does Heredity carry in the CBSE Class 10 Science exam?
Heredity is part of the World of Living unit, which carries 25 marks in the official syllabus. In the analysed papers it had about 3.9 questions per paper.
Do questions from Heredity repeat in board exams?
Yes — 6 question patterns from this chapter appeared in two or more past board or official sample papers. They are listed on this page with the years they were asked.