--- title: "NCERT Solutions for Class 10 Science Chapter 8 Heredity (2026-27)" url: https://www.swavid.com/science/class/10/chapter/heredity/ncert-solutions dateModified: 2026-10-07T16:46:01+00:00 --- # NCERT Solutions for Class 10 Science Chapter 8 Heredity (2026-27) This chapter covers questions testing students' understanding of heredity, genetic variations, Mendelian inheritance, and sex determination. Free PDF (5 pages): https://www.swavid.com/api/seo/pdf/ncert/science/class-10/swavid-ncert-solutions-class-10-science-chapter-8-heredity-e8e4ee8b72.pdf ## QUESTIONS ### Question 1 *3 marks · Short answer* If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier? **Solution** 1. Trait B is likely to have arisen earlier in the population. 2. In an asexually reproducing species, variations arise due to small inaccuracies in DNA copying. 3. As the population reproduces over generations, new traits accumulate and spread, so a trait present in a higher percentage (60%) has been present for a longer time than one present in a lower percentage (10%). **Answer:** Trait B is likely to have arisen earlier. > Common mistake: Confusing higher percentage with lesser time or assuming sexual reproduction. ### Question 2 *3 marks · Short answer* How does the creation of variations in a species promote survival? **Solution** 1. Variations provide different kinds of advantages to individuals in a species depending on their environment. 2. For example, bacteria that possess variations enabling them to withstand heat will survive better during a heat wave. 3. Thus, the creation of variations forms the basis of adaptation and ensures the survival of species against environmental changes. **Answer:** Variations help individuals adapt and survive better against environmental changes such as temperature fluctuations. > Common mistake: Failing to connect variations with environmental factors like temperature or habitat change. ## QUESTIONS ### Question 1 *3 marks · Short answer* How do Mendel’s experiments show that traits may be dominant or recessive? **Solution** 1. Mendel crossed tall pea plants with short pea plants and found that all $F_1$ progeny were tall, showing no medium-height or blended characteristics. 2. When these $F_1$ tall plants were self-pollinated to produce the $F_2$ generation, both tall and short plants appeared in a ratio of $3:1$. 3. This indicates that both tallness and shortness traits were inherited in $F_1$ plants, but only the tallness trait was expressed, proving that tallness is dominant and shortness is recessive. **Answer:** Mendel's experiments with tall and short pea plants showed that $F_1$ progeny only display one parental trait (dominant), while the other hidden trait (recessive) reappears in the $F_2$ generation. > Common mistake: Stating that recessive traits are completely lost in the $F_1$ generation instead of remaining unexpressed. ### Question 2 *3 marks · Short answer* How do Mendel’s experiments show that traits are inherited independently? **Solution** 1. Mendel bred pea plants with two contrasting characteristics, such as round-seeded green plants and wrinkled-seeded yellow plants. 2. In the $F_2$ generation, along with parental combinations, he observed new combinations of traits, such as round-seeded yellow plants and wrinkled-seeded green plants. 3. This independent recombination of seed shape and seed colour traits demonstrates that two separate traits are inherited independently of each other. **Answer:** Mendel showed independent inheritance by crossing plants with two pairs of contrasting characters and observing new combinations of traits in the $F_2$ generation. > Common mistake: Confusing monohybrid cross results with dihybrid cross independent assortment. ### Question 3 *3 marks · Short answer* A man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not? **Solution** 1. No, this information is not enough to determine which blood group trait is dominant. 2. A child receives one gene copy from each parent, so the daughter with blood group O must have inherited one O gene from her father and one O gene from her mother. 3. Since the father has blood group A, he must possess an AO genotype, but we cannot ascertain dominance between blood group A and O from this single cross without further pedigree or progeny data. **Answer:** No, the information is insufficient because both parents must contribute genes for blood group O to appear in the daughter, and the father's blood group A could be heterozygous. > Common mistake: Assuming the parent with blood group A is homozygous dominant without checking alternative allele combinations. ### Question 4 *3 marks · Short answer* How is the sex of the child determined in human beings? **Solution** 1. Human beings have 23 pairs of chromosomes, out of which one pair consists of sex chromosomes. 2. Women have a perfect pair of sex chromosomes ($XX$), while men have a mismatched pair ($XY$). 3. All children inherit an $X$ chromosome from their mother, so the sex of the child is determined by what they inherit from their father: an $X$ chromosome makes a girl ($XX$), and a $Y$ chromosome makes a boy ($XY$). **Answer:** The sex of a child in human beings is determined by the paternal sex chromosome, where an inherited $X$ chromosome results in a girl and a $Y$ chromosome results in a boy. > Common mistake: Stating that the mother contributes to the sex determination of the child. ## EXERCISES ### Question 1 *1 mark · MCQ* A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short. This suggests that the genetic make-up of the tall parent can be depicted as - TTWW - TTww - TtWW - TtWw **Solution** 1. The progeny all bore violet flowers, meaning violet (W) is dominant over white (w) and the parent must be homozygous dominant for flower color (WW). 2. Almost half of the progeny were short, indicating a test cross ratio where the tall parent is heterozygous for height (Tt). 3. Therefore, the genetic make-up of the tall parent is TtWW, making option (c) correct. **Answer:** (c) TtWW > Common mistake: Confusing homozygous and heterozygous conditions for the traits. ### Question 2 *3 marks · Short answer* A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not? **Solution** 1. Given that children with light-coloured eyes are likely to have parents with light-coloured eyes. 2. No, this information alone is not enough to conclude whether light eye colour is dominant or recessive. 3. Both dominant and recessive traits can run in families; a recessive trait requires both parents to carry the allele, which frequently happens if the trait is common in that population. **Answer:** We cannot say whether the light eye colour trait is dominant or recessive based only on this observation, because both dominant and recessive traits can be inherited by children from their parents. > Common mistake: Assuming that traits seen frequently in children or parents are always dominant. ### Question 3 *5 marks · Long answer* Outline a project which aims to find the dominant coat colour in dogs. **Solution** 1. Select a male dog with one coat colour (e.g., black) and a female dog with a contrasting coat colour (e.g., brown) to perform a breeding experiment. 2. Observe the coat colour of the puppies in the first generation (F1 progeny). 3. The coat colour that appears in all F1 progeny is the dominant trait, while the one that remains hidden is the recessive trait. 4. Cross the F1 progeny among themselves to obtain the second generation (F2 progeny). 5. Count the proportion of traits in the F2 generation to confirm the dominance pattern, as recessive traits reappear in the F2 generation. **Answer:** A breeding project involving dogs with contrasting coat colours can determine dominance by observing which trait is expressed in the F1 generation and which reappears in the F2 generation. > Common mistake: Forgetting to breed the F1 generation to see the F2 progeny where recessive traits become visible. ### Question 4 *3 marks · Short answer* How is the equal genetic contribution of male and female parents ensured in the progeny? **Solution** 1. Sexually reproducing organisms have two sets of chromosomes, one inherited from each parent. 2. During gamete formation in parents, meiosis ensures that each germ cell (sperm or egg) receives only one complete set of chromosomes. 3. When the male and female germ cells fuse during fertilization, the normal two sets of chromosomes are restored in the zygote, ensuring equal genetic contribution from both parents. **Answer:** Equal genetic contribution is ensured because each germ cell contains only one set of chromosomes, and the fusion of a sperm and an egg restores the two sets of chromosomes in the progeny. > Common mistake: Stating that body cells contribute directly instead of germ cells. ## Frequently asked questions ### How many questions are there in the NCERT Solutions for Class 10 Science Chapter 8 Heredity on SwaVid? This chapter contains a total of 10 questions across its sections and exercises for the 2026-27 academic session. You can access SwaVid's free PDF and step-by-step solutions for all of them on this page only. ### Which topics do the questions in this chapter cover? The questions cover important concepts like the accumulation of variation, population frequency, survival advantage of variations, and blood group inheritance. They also explore dominant and recessive traits, independent inheritance, sex determination in humans, and Mendelian crosses. ### What is the hardest question type in this chapter and how should I approach it? Long answer questions involving genetics and Mendelian crosses are often considered the hardest by students. To approach them, you should first clearly identify the parental genotypes, draw accurate Punnett squares, and then write down the phenotypic and genotypic ratios step by step. ### How can I write answers to score full marks in Class 10 board exams for this chapter? To secure full marks, structure your answers with clear scientific terms and bullet points where necessary. For heredity problems, always state your assumptions, show the cross clearly, and explicitly mention the final ratio or conclusion. ### Is the free PDF for these NCERT solutions available for download? Yes, the complete free PDF and detailed step-by-step solutions for Class 10 Science Chapter 8 are available on this page only. You can use these resources to revise the chromosomal mechanism of inheritance and practice for your exams effectively. ## Related pages - [Heredity: CBSE previous year questions](https://www.swavid.com/cbse/class-10/science/pyq/heredity) - [Class 10 Science chapters](https://www.swavid.com/science/class/10) Solutions written by SwaVid, a personal AI tutor for Class 6 to 10 Maths and Science. Practise this chapter free: https://www.swavid.com/start/student