Page 1: Introduction

Heredity: transmission of traits from parents to offspring.

Variation: differences among offspring.

Genetics: study of heredity and variation.

Mendel: father of genetics.

Page 2: Mendel’s Experiments

Used pea plants (7 contrasting traits).

Monohybrid cross: one trait.

Dihybrid cross: two traits.

Page 3: Monohybrid Cross

Tall (TT) × dwarf (tt) → F1 all tall (Tt)

F1 self → F2 3 tall : 1 dwarf (phenotypic)

Genotypic 1:2:1

Page 4: Mendel’s Laws

• Law of Dominance: dominant trait masks recessive.
• Law of Segregation: alleles separate during gamete formation.
• Law of Independent Assortment: genes for different traits assort independently.

Page 5: Dihybrid Cross

Round yellow (RRYY) × wrinkled green (rryy) → F1 all Ry (round yellow)

F2 phenotypic 9:3:3:1

Law of independent assortment.

Page 6: Terms

• Gene, allele
• Homozygous, heterozygous
• Phenotype, genotype
• Dominant, recessive

Page 7: Sex Determination

Humans: 23 pairs chromosomes, 22 autosomes + 1 sex.

Female XX, male XY.

Father determines sex (50% chance boy/girl).

Page 8: Acquired vs Inherited Traits

Inherited: genetic (eye colour).

Acquired: during life (skills, scars) — not passed to offspring.

Page 9: Key Points Summary

• Mendel’s three laws
• Monohybrid 3:1, dihybrid 9:3:3:1
• Sex determination in humans
• Inherited vs acquired

Page 10: Practice Questions - Easy (1-10)

1. Law of segregation.
2. Phenotypic ratio monohybrid.
3. Sex chromosomes female.
4. Dominant trait meaning.
5. Dihybrid ratio.
6. Homozygous tall.
7. Acquired trait example.
8. Mendel’s plant.
9. Independent assortment.
10. F1 generation all dominant.

Page 11: Practice Questions - Medium (11-20)

11. Cross tall heterozygous × dwarf.
12. Dihybrid cross phenotypic ratio explanation.
13. Sex determination in humans.
14. Genotypic ratio monohybrid F2.
15. Why Mendel chose pea.
16. Punnett square for Tt × Tt.
17. Inherited trait example.
18. Law of dominance example.
19. Probability of girl child.
20. Cross RrYy × RrYy ratio.

Page 12: Practice Questions - Hard (21-30)

21. Explain Mendel’s laws with example.
22. Punnett square dihybrid detailed.
23. Board level monohybrid cross.
24. Difference inherited and acquired.
25. Sex determination in birds hint.
26. Multiple allele hint.
27. Variation importance.
28. Mendel experiment significance.
29. Genotype phenotype difference.
30. Real-life application genetics.

Page 13: Mendel’s Laws Table

Law, statement, example.

Page 14: Common Mistakes

• Wrong ratio in F2
• Confusing genotype phenotype
• Mother determines sex
• Forgetting 9:3:3:1
• Missing independent assortment

Page 15: Previous Year Questions

Cross ratios, laws, sex determination.

Page 16: Exam Tips

• Draw Punnett square neatly
• Write ratios clearly
• State laws exactly
• Give examples
• Memorise 3:1 and 9:3:3:1

Page 17: Quick Revision Sheet

Laws, ratios, sex determination.

Page 18: Final Motivation

Chapter 9 complete! Heredity is scoring with Punnett practice.

Master ratios and laws.

Class 10 Science unstoppable 🦖

Page 19: Extra Crosses

Monohybrid and dihybrid Punnett.

Page 20: Sex Determination

Human and other organisms hint.

Page 21: Mendel’s Traits

7 contrasting pairs.

Page 22: Board Pattern

Cross and ratio questions.

Page 23: Extra Practice

More crosses.

Page 24: Variation

Importance in evolution hint.

Page 25: Acquired Traits

Not inherited explanation.

Page 26: Punnett Square Tips

How to draw correctly.