Mnemonics: Heredity | Science Class 10 PDF Download

1. Accumulation of Variation During Reproduction

Mnemonic: "Big Cats Never Nap"

Example: Tigers and Stripes

• Basic Design: A tiger cub looks like its parents, inheriting the same body structure.
• Changes: Some cubs may have slightly different stripe patterns due to small DNA changes.
• Next Generation: When these cubs grow up and reproduce, their offspring inherit these stripe variations.
• New Variations: Over time, tigers in different areas may develop unique stripe patterns, helping them blend better into their surroundings.

Key Idea: Small changes in each generation add up, leading to noticeable dif

ferences over time.Creation of diversity over succeeding generation

2. Heredity

Mnemonic: "PPT – Parents Pass Traits"

Imagine parents gifting traits like a slideshow presentation:

• Parents pass eye color, height, and hair type.
• Partially mixed: Some features from the mother, some from the father.
• Traits vary, but the basic design stays the same.

Key Idea: Traits are inherited from parents, but unique variations appear.

Parents Pass Traits

3. Mendel’s Laws of Inheritance

Monohybrid Cross (Single Trait)

Mnemonic: "TGP – Tall Genes Predict"

Think of Mendel as a scientist predicting plant height:

• Tall trait is dominant.
• Genotypic Ratio (F2) = 1:2:1 (TT, Tt, tt).
• Phenotypic Ratio (F2) = 3:1 (Tall: Short).

Key Idea: Dominant traits appear in the first generation, while recessive traits reappear later.                                                         Monohybrid Cross

Dihybrid Cross (Two Traits)

Mnemonic: "RRYG 9-3-3-1"

Picture a vegetable market with pea varieties:

• 9 Round Yellow Peas (Most Common).
• 3 Round Green Peas.
• 3 Wrinkled Yellow Peas.
• 1 Wrinkled Green Pea (Rare).

Key Idea: Traits assort independently, leading to different combinations.Dihybrid Cross

4. Sex Determination in Humans

Mnemonic:  "Mom Always Gives X, Dad Decides Next"

• Mom (Mother) always gives X chromosome
• Dad (Father) gives either X or Y
• If Dad gives X → XX (Girl)
• If Dad gives Y → XY (Boy)

Key Idea: The father's chromosome determines the sex of the child.Sex Determination in Humans