CBSE Class 10 Science: Heredity | Important Concept-Based Questions

Understand the Core Concepts of Genetics and Inheritance Simplified by BACE IIT JEE

🔬 Introduction: Understanding Heredity

Heredity is the process through which traits and characteristics are transmitted from one generation to another. This chapter lays the foundation for understanding genetics — the branch of biology dealing with inheritance and variation of traits. For CBSE Class 10 students, this topic is crucial as it combines both conceptual and application-based questions in board examinations.

In this article, we will explore important concept-based questions from this chapter, simplified explanations, and quick recall notes to boost your exam preparation. Let’s decode the mysteries of heredity in a simple yet scientific way.

🧬 Key Concepts of Heredity

1. Genes and Chromosomes

Genes are the basic units of inheritance. They are located on chromosomes inside the cell nucleus. Each gene carries information to determine specific traits like height, eye colour, or blood group.

2. Mendel’s Experiments

Gregor Johann Mendel conducted experiments on pea plants and established the laws of inheritance. His observations formed the basis of modern genetics. Mendel’s experiments involved monohybrid and dihybrid crosses that helped in discovering the patterns of inheritance.

3. Dominant and Recessive Traits

Traits that are expressed in an organism even if one allele is present are dominant traits. Traits that appear only when both alleles are identical are called recessive traits. For example, in pea plants, tallness (T) is dominant over dwarfness (t).

4. Genotype and Phenotype

Genotype refers to the genetic constitution of an organism (e.g., TT or Tt), while Phenotype refers to the physical appearance (e.g., Tall or Dwarf). Understanding these helps in predicting the probability of traits in offspring using a Punnett square.

5. Sex Determination

Sex determination in humans depends on the type of chromosomes inherited. Females have XX chromosomes, while males have XY. The sperm determines the child’s sex during fertilization.

6. Evolutionary Importance of Heredity

Heredity ensures continuity of traits while allowing variations. Variations contribute to the process of evolution, leading to the survival of species better adapted to their environment.

📘 Important Concept-Based Questions and Answers

Q1. Who is known as the Father of Genetics? What were his key contributions?

A1. Gregor Johann Mendel is known as the Father of Genetics. He conducted experiments on pea plants and discovered the fundamental laws of inheritance — the Law of Dominance, the Law of Segregation, and the Law of Independent Assortment.

Q2. Explain the difference between dominant and recessive traits with an example.

A2. Dominant traits are expressed even when only one copy of the allele is present (Tt = Tall). Recessive traits appear only when both alleles are identical (tt = Dwarf). Example: In pea plants, tallness (T) is dominant over dwarfness (t).

Q3. What is a monohybrid cross? Illustrate with an example.

A3. A monohybrid cross involves the study of inheritance of a single trait. Example: Crossing a tall pea plant (TT) with a dwarf pea plant (tt) produces offspring (Tt) that are all tall. This helps in understanding the Law of Segregation.

Q4. Define genotype and phenotype.

A4. Genotype is the genetic makeup of an organism (TT, Tt, or tt), while phenotype is the observable characteristic (Tall or Dwarf).

Q5. What is the role of variation in evolution?

A5. Variations are differences among individuals of the same species. They play a vital role in evolution by allowing better adaptation and survival of the fittest in changing environments.

Q6. How does sex determination take place in humans?

A6. The sex of a child is determined by the type of sperm that fertilizes the egg. If an X-bearing sperm fertilizes the ovum, the child will be female (XX). If a Y-bearing sperm fertilizes the ovum, the child will be male (XY).

Q7. State Mendel’s three laws of inheritance.

A7. Law of Dominance – One factor (allele) dominates over the other.
Law of Segregation – Each pair of alleles separates during gamete formation.
Law of Independent Assortment – Alleles of different traits assort independently during gamete formation.

🧠 Concept Application: Solved Board Pattern Questions

Q8. Why does a child look similar to its parents but not identical?

A8. A child inherits half the genes from each parent. The combination of genes creates similarities but not exact resemblance due to genetic recombination and variation.

Q9. Explain how traits are inherited from parents to offspring using an example of eye colour.

A9. Eye colour is determined by multiple genes. If both parents carry dominant alleles for brown eyes, the child will likely have brown eyes. The variation occurs when combinations of dominant and recessive alleles mix differently.

Q10. How does heredity differ from variation?

A10. Heredity transmits parental traits to offspring, while variation introduces differences among individuals of the same species, which is vital for evolution.

📝 Quick Revision Notes

• Gene: Unit of heredity that transmits traits.
• Allele: Alternate form of a gene responsible for variation in traits.
• Homozygous: Same type of alleles (TT or tt).
• Heterozygous: Different alleles (Tt).
• Genotype: Genetic composition.
• Phenotype: Observable features.
• Chromosomes: Structures carrying genes inside the nucleus.

🎯 Tips to Score Full Marks in Heredity (Board Exam)

• Understand the Mendelian laws and their applications clearly.
• Practice drawing and labeling Punnett squares neatly.
• Memorize definitions of key terms like gene, allele, and genotype.
• Revise all NCERT In-text Questions and Board Pattern Questions.
• Use flowcharts for inheritance patterns for quick recall.

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Our faculty ensures that every student understands the logic behind scientific principles and connects them with real-world applications — a key differentiator that leads to board and competitive exam success.

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