A. What is Heredity?

Heredity is the process by which traits are passed from parents to offspring through genes.
It explains why children resemble their parents in features like eye color, height, or blood group.

B. Basic Terms in Heredity

• Gene: Unit of heredity that controls a trait
• Chromosome: Structure in the nucleus carrying genes
• DNA (Deoxyribonucleic Acid): Chemical substance of genes
• Trait: Observable characteristic (e.g., tallness, hair type)

C. Mendel and Laws of Inheritance

The study of heredity was pioneered by Gregor Mendel.

Key Laws:

• Law of Dominance: One trait (dominant) masks another (recessive)
• Law of Segregation: Alleles separate during gamete formation
• Law of Independent Assortment: Traits are inherited independently

D. Dominant and Recessive Traits

• Dominant Trait: Expressed even if one allele is present (T)
• Recessive Trait: Expressed only when both alleles are present (tt)

👉 Example:

• Tall (T) is dominant
• Dwarf (t) is recessive

E. Monohybrid Cross (Simple Inheritance)

A cross involving one pair of contrasting traits.

👉 Example:
TT (Tall) × tt (Dwarf)
Result: All offspring are Tt (Tall)

F. Importance of Heredity

• Helps understand family resemblance
• Useful in plant and animal breeding
• Helps study genetic diseases
• Foundation for modern genetics

G. Why This Chapter Matters

This chapter is essential because it:

• Builds the base for genetics and evolution
• Frequently appears in entrance exams
• Develops logical and analytical thinking

H. Scientific Learning Tip

• Practice Punnett squares regularly
• Focus on genetic terms and definitions
• Understand concepts instead of memorizing

I. Quick Revision

• Heredity = transfer of traits
• Gene = unit of inheritance
• Mendel = father of genetics
• Dominant vs Recessive traits
• Monohybrid cross basics