NCERT Class 12 Biology Chapter 4 Principles of Inheritance and Variation MCQs & PYQ

In NCERT Class 12 Biology Chapter 4, titled "Principles of Inheritance and Variation," students learn about the fundamental concepts of genetics. The chapter explains Mendel's laws of inheritance, the chromosomal theory of inheritance, and the causes and types of genetic variation. Topics like linkage, crossing over, mutations, and genetic disorders are also explored in detail. This chapter lays the groundwork for understanding complex genetic traits and heredity.

This article provides a comprehensive resource for exam preparation. It includes sample MCQs and subjective questions for CBSE and CUET, alongside downloadable PDFs of Class 12 Biology Chapter 4 MCQs and previous year questions for detailed practice of NCERT Class 12 Principles of Inheritance and Variation.

NCERT Class 12 Biology Chapters
Chapter 1: Sexual Reproduction in Flowering Plants	Chapter 2: Human Reproduction
Chapter 3: Reproductive Health	Chapter 5: Molecular Basis of Inheritance
Chapter 6: Evolution	Chapter 7: Human Health and Disease
Chapter 8: Microbes in Human Welfare	Chapter 9: Biotechnology: Principles and Processes
Chapter 10: Biotechnology and its Applications	Chapter 11: Organisms and Populations
Chapter 12: Ecosystem	Chapter 13: Biodiversity and Conservation

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Class 12 Biology Chapter 4 MCQs

This question bank includes previous years' CUET and CBSE MCQs, along with questions curated by subject experts. Below are 5 sample multiple-choice questions (MCQs) for Class 12 Biology Chapter 4: Principles of Inheritance and Variation. For the full set of 50 questions, download the PDF using the link provided below.

1.	Two statements are given one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below. Assertion (A): In a monohybrid cross between tall plants and dwarf plants, the F₂ generation showed tall and dwarf plants in the ratio of 3 : 1. Reason (R): There is no blending of traits/characters in the F₂generation. (a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A). (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A). (c) Assertion (A) is true, but Reason (R) is false. (d) Assertion (A) is false, but Reason (R) is true.
2.	Three genes R, S and T are located on the same chromosome. If the recombination percentage between R and S is 20%, R and T is 35% and S and T is 15% respectively, can you predict the correct order of these genes on the chromosome? Which of the following shows the correct sequence of the genes on the chromosome? (a) R T S (b) R S T (c) S R T (d) S T R
3.	Two statements are given one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below. Assertion (A): In humans the genotype with all the dominant alleles (AABBCC) will have the darkest skin colour. Reason (R): In a polygenic trait, phenotype reflects the contribution of each allele. (a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A). (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A). (c) Assertion (A) is true, but Reason (R) is false. (d) Assertion (A) is false, but Reason (R) is true.
4.	Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below. Assertion (A): Birds like pigeon have heterogametic females whereas the males are homogametic. Reason (R): In pigeons, females have Z and W sex chromosomes whereas males have ZZ sex chromosomes. (a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A). (b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A). (c) Assertion (A) is true, but Reason (R) is false. (d) Assertion (A) is false, but Reason (R) is true.
5.	Choose the set of sex determining chromosomes that indicates the correct sex of the respective organism. (a) Homozygous sex chromosomes (ZZ) determine female sex in birds (b) XO type of sex chromosomes determine male sex in grasshoppers (c) XXY condition in humans, as found in Turner Syndrome, determines male sex (d) Homozygous sex chromosomes (XX) produce male sex in Drosophila

Class 12 Biology Chapter 4 Subjective Questions Without Solutions

This question bank includes previous years' CBSE subjective questions (2 marks and above) without solutions, along with expert-curated questions. Below are 5 sample subjective questions for Class 12 Biology Chapter 4: Principles of Inheritance and Variation. To access all questions, download the PDF from the link provided below.

1.	(i) A true breeding tall pea plant with round seeds is crossed with a recessive dwarf pea plant having wrinkled seeds. Work out the cross up to F₂ generation giving the phenotypic ratios of F₁ and F₂ generation respectively. (ii) State the Mendelian principle that can be derived only with the help of such a cross. (CBSE 2023, 5M)
2.	A homozygous tall pea plant with green seeds is crossed with a homozygous dwarf pea plant with yellow seeds. (i) Write the possible phenotype and genotype of F₁ generation. (ii) State the laws of Mendel that are proved true by the F₁ generation. (iii) Mention the F₂ phenotypic ratio along with their possible phenotypes. (iv) Write the genotypes of the male and female gametes produced by F₁ progeny. (CBSE 2023, 5M)
3.	You are given a tall pea plant with green seeds. The genotype of this plant is unknown. You are allowed to do only ‘selfing’ of these plants to find out the genotype of the given plant. Work out all possible crosses and show how you would determine the genotype of the given plant. (CBSE 2023, 5M)
4.	Describe the dihybrid cross upto F₂ generation as conducted by Gregor Mendel using pure lines of Garden Pea for characters seed shape and seed colour. (CBSE 2023, 5M)
5.	By using Punnett square depict the genotypes and phenotypes of test crosses (where green pod colour (G) is dominant over yellow pod colour (g)) in Garden pea with unknown genotype. (CBSE 2023, 2M)

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Sub Areas of Chapter 4: Principles of Inheritance and Variation

Chapter Name	Sub Topics
Principles of Inheritance and Variation	4.1 Introduction
	4.2 Mendel’s Laws of Inheritance
	4.3 Deviations from Mendel’s Laws
	4.4 Chromosomal Theory of Inheritance
	4.5 Linkage and Crossing Over
	4.6 Mutations and Genetic Variation
	4.7 Sex Determination
	4.8 Genetic Disorders: Chromosomal and Mendelian

Review of NCERT Class 12 Biology Chapter 4

In NCERT Class 12 Biology Chapter 4, "Principles of Inheritance and Variation," students explore the basics of heredity and genetics. This chapter discusses Mendel's pioneering work on inheritance patterns, deviations from Mendelian ratios, and the chromosomal basis of inheritance. It also covers key concepts such as genetic mutations, sex determination, and genetic disorders, providing an in-depth understanding of how traits are passed from one generation to the next.

By practicing MCQs and subjective questions, students can strengthen their understanding of genetic principles and their applications. Mastery of this chapter is essential for academic success and provides a solid foundation for future studies in genetics, biotechnology, and medicine.

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