Chapter Overview & Weightage
- Marks in Boards: 10–14 marks (highest in Genetics unit – usually 2–3 questions + numerical/pedigree)
- Repeated Topics: Mendel's laws, monohybrid/dihybrid crosses, incomplete dominance, co-dominance, linkage, crossing over, pedigree analysis, chromosomal disorders, sex determination.
- Difficulty: Moderate to high • Heavy on crosses (Punnett square), pedigree, numericals (probability, gene frequency).
- Trend (2021–2025): 1 pedigree/numerical (3–5 marks) + 1 long answer (5 marks) on Mendel's laws/linkage + MCQs on disorders & sex determination.
Most Important & Repeated Questions (2021–2025)
- Repeated 5–6 times: State and explain Mendel's Law of Segregation and Independent Assortment with examples. (5 marks)
- Repeated 4–5 times: Solve a dihybrid cross (e.g., round yellow × wrinkled green) and give phenotypic & genotypic ratio. (5 marks)
- Repeated 4 times: Explain incomplete dominance and co-dominance with examples (e.g., snapdragon flower, blood groups). (3 marks)
- Repeated 3–4 times: What is linkage? Explain crossing over with diagram. (5 marks)
- Repeated 3 times: Solve pedigree analysis: Determine mode of inheritance (autosomal dominant/recessive, X-linked). (3–5 marks)
- Repeated 3 times: Explain sex determination in humans. What is Barr body? (3 marks)
- Repeated 2–3 times: What are chromosomal disorders? Explain Down's syndrome & Klinefelter's syndrome. (3 marks)
- Assertion-Reason (2023–2025): Assertion: Law of segregation is due to separation of alleles during meiosis. Reason: Alleles are present in homologous chromosomes. (Both true, reason explains – repeated 2x)
Important Keywords & Concepts to Memorize
- Gene, allele, locus, homozygous, heterozygous, dominant, recessive, genotype, phenotype, monohybrid cross, dihybrid cross, Punnett square, test cross, back cross, incomplete dominance, co-dominance, multiple alleles (ABO blood group), pleiotropy, polygenic inheritance, linkage, crossing over, recombination frequency, pedigree analysis, Mendel's laws (segregation, independent assortment, dominance), chromosomal theory of inheritance, sex determination (XX-XY, ZW-ZZ), chromosomal disorders (Down's, Klinefelter's, Turner's), Barr body, sickle cell anaemia, phenylketonuria.
Exam Strategy for Chapter 5 (2026 Boards)
- Focus: Punnett square for monohybrid/dihybrid crosses – practice 5 daily
- High-scoring: Pedigree analysis (3–5 marks) + explain mode of inheritance
- Time: 8–10 minutes per 5-mark question (cross + explanation)
- Tip: Draw Punnett square neatly – label genotypes & phenotypes
- Repeated: Incomplete dominance vs co-dominance difference (2–3 marks)
This is Chapter 5 complete PYQ analysis.
If you want Chapter 6 or any other chapter, just say the chapter number or name.