Class 12 Biology — Chapter 4: Principles of Inheritance and Variation
92 practice questions · 31 Easy · 31 Medium · 30 Hard
Practise Class 12 Biology Chapter 4, "Principles of Inheritance and Variation", with 92 NCERT-aligned multiple-choice questions. The set is split into 31 Easy, 31 Medium and 30 Hard questions, so you can warm up on the fundamentals and then push into the exam-level problems that separate top scorers in CBSE Board exams and NEET UG.
"Principles of Inheritance and Variation" is one of the chapters where diagram-based recall, terminology and NCERT line-by-line accuracy really pays off. Each MCQ on this chapter is timed and uses exam-grade marking (+2 correct, −1 wrong, 0 skipped), training the same accuracy-under-pressure that real papers demand. Every question carries a short explanation, so a wrong answer becomes a quick lesson rather than a dead end — the fastest way to close gaps before a test.
Use this chapter as targeted revision: attempt the Easy set first to confirm your basics on Principles of Inheritance and Variation, then move to Medium and Hard to test application and problem-solving. Your accuracy, streaks and XP save automatically, and the chapter feeds into your overall Class 12 Biology mastery score. A few sample questions are shown below; sign in free to practise all 92.
Key concepts: Principles of Inheritance and Variation (Class 12 Biology)
This chapter covers Mendel's laws of inheritance, deviations like incomplete dominance and epistasis, chromosomal theory, linkage, sex determination and genetic disorders.
- Mendel's laws
- Law of dominance, law of segregation (factors separate in gametes) and law of independent assortment.
- Monohybrid & dihybrid ratios
- A monohybrid cross gives a 3:1 phenotypic ratio; a dihybrid cross gives 9:3:3:1.
- Deviations from Mendel
- Incomplete dominance (1:2:1 phenotype), co-dominance (e.g. AB blood group), and multiple alleles.
- Linkage & sex determination
- Linked genes are inherited together; sex is determined by XX/XY (humans) or XX/XO systems.
- Genetic disorders
- Mendelian (haemophilia, sickle-cell anaemia, colour blindness) and chromosomal (Down's, Turner's, Klinefelter's syndromes).
Key formulas — Principles of Inheritance and Variation
💡 Exam tips for Principles of Inheritance and Variation
- Incomplete dominance changes the phenotypic ratio to 1:2:1 (same as the genotypic ratio).
- Haemophilia and colour blindness are X-linked recessive — more common in males.
Sample questions
The father of modern genetics is:
Gregor Mendel formulated the laws of inheritance using pea plant experiments.
In a monohybrid cross between two heterozygotes (Tt × Tt), the F₂ phenotypic ratio is:
Tt × Tt → 1 TT : 2 Tt : 1 tt. Phenotype ratio = 3 dominant : 1 recessive.
Mendel's law of segregation is based on which cellular event?
Allele pairs separate when homologous chromosomes separate in anaphase I of meiosis.
Principles of Inheritance and Variation — FAQs
What are the key concepts in Class 12 Biology Principles of Inheritance and Variation?+
This chapter covers Mendel's laws of inheritance, deviations like incomplete dominance and epistasis, chromosomal theory, linkage, sex determination and genetic disorders. Key ideas include Mendel's laws, Monohybrid & dihybrid ratios, Deviations from Mendel, Linkage & sex determination, Genetic disorders.
What does Class 12 Biology Chapter 4 (Principles of Inheritance and Variation) cover on XamBaaz?+
It covers 92 NCERT-aligned MCQs on "Principles of Inheritance and Variation" — 31 Easy, 31 Medium and 30 Hard — each with a timed quiz and an instant explanation, suitable for CBSE Board exams and NEET UG.
Are these "Principles of Inheritance and Variation" questions free to practise?+
Yes — sign in with Google to practise "Principles of Inheritance and Variation" free. Full unlimited access is ₹999/year (limited-time launch price), with no per-chapter charges.
How should I revise "Principles of Inheritance and Variation" for the exam?+
Start with the Easy quiz to confirm your fundamentals, then attempt Medium and Hard for application-level practice. Review each explanation, retry the questions you miss, and track your accuracy on this chapter until it is consistently high.
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