Cheat sheet · NEET Preparation Botany
Principles of Inheritance and Variation cheat sheet
The whole chapter on one page: key formulas, facts and the points to remember, for quick revision before a test.
NEET · Botany
Cheat sheet
Class 12 · Chapter 3Principles of Inheritance and Variation
Mendel's ratios: monohybrid 3 : 1, dihybrid 9 : 3 : 3 : 1, test cross 1 : 1.
1. Mendel's Laws
- Law of dominance.
- Law of segregation (purity of gametes).
- Law of independent assortment (dihybrid cross).
2. Deviations
| Pattern | Example | F₂ ratio |
|---|---|---|
| Incomplete dominance | snapdragon flower colour | 1 : 2 : 1 |
| Co-dominance | ABO blood group (Iᴬ Iᴮ) | 1 : 2 : 1 |
| Multiple alleles | ABO (3 alleles) | — |
| Pleiotropy | phenylketonuria | — |
| Polygenic | human skin colour | continuous |
3. Chromosomal Theory
- Sutton and Boveri.
- Morgan (Drosophila): linkage and recombination.
- Sex determination: XX–XY (humans), XX–XO (grasshopper), ZW–ZZ (birds).
4. Disorders
| Disorder | Type |
|---|---|
| Haemophilia, colour blindness | X-linked recessive |
| Sickle-cell anaemia | autosomal recessive (Glu → Val) |
| Thalassaemia | autosomal recessive |
| Down's syndrome | trisomy 21 |
| Klinefelter's | XXY |
| Turner's | XO |
5. Key Points
- Test cross reveals genotype.
- Linked genes are inherited together.
- Pedigree analysis traces traits.
- Mutations: point, frameshift.
Remember: 3 laws | deviations | sex determination | disorders
Principles of Inheritance and Variation: questions and notes
More NEET Preparation Botany cheat sheets
- The Living World
- Biological Classification
- Plant Kingdom
- Morphology of Flowering Plants
- Anatomy of Flowering Plants
- Cell: The Unit of Life
- Cell Cycle and Cell Division
- Photosynthesis in Higher Plants
- Respiration in Plants
- Plant Growth and Development
- Sexual Reproduction in Flowering Plants
- Principles of Inheritance and Variation
- Molecular Basis of Inheritance
- Microbes in Human Welfare
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
Practise Principles of Inheritance and Variation
Sign up free to practise the full chapter. Questions you get wrong come back until you've mastered them.
Start practising freeFree to start · No credit card needed