Class 12 Biology Chapter 4 Principles of Inheritance and Variation Notes [Handwritten Notes PDF]
Class 12 Biology Chapter 4 – Principles of Inheritance and Variation Notes are provided here in clear, well-structured handwritten format. These notes cover Mendelian genetics, gene interactions, linkage & recombination, sex determination, pedigree analysis, and chromosomal disorders—perfect for CBSE Boards and NEET (UG) preparation.
Topics Covered
- Mendel’s Experiments, Monohybrid & Dihybrid Crosses
- Mendel’s Laws – Dominance, Segregation, Independent Assortment
- Test Cross & Back Cross; Punnett Square
- Gene Interactions – Incomplete Dominance, Codominance, Multiple Alleles (ABO)
- Pleiotropy & Polygenic Inheritance
- Chromosomal Theory of Inheritance (Sutton & Boveri)
- Linkage and Recombination (Morgan & Sturtevant); Crossing Over & Mapping
- Sex Determination Mechanisms (XX–XY, XX–XO, ZZ–ZW, Haplodiploidy)
- Sex-linked Inheritance – Hemophilia, Color Blindness; Criss-cross Inheritance
- Mutations – Gene & Chromosomal; Pedigree Analysis
- Chromosomal Disorders – Down’s, Klinefelter’s, Turner’s, Cri-du-chat (brief)
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FAQs
1. Are these notes handwritten? Yes, they are neat handwritten notes for quick learning and revision.
2. Do these notes explain Mendel’s laws? Yes, all three laws with monohybrid/dihybrid examples are covered.
3. What is the difference between incomplete dominance and codominance? Both are explained with classic examples (snapdragon/roan cattle & ABO blood groups).
4. Is test cross included? Yes, test cross and back cross with genotype deduction are covered.
5. Are linkage and recombination discussed? Yes, concepts by Morgan & Sturtevant, crossing over, and gene mapping are included.
6. Is sex determination part of this chapter? Yes, XX–XY, XX–XO, ZZ–ZW, and haplodiploidy mechanisms are summarized.
7. Do these notes include sex-linked traits? Yes, hemophilia, color blindness, and criss-cross inheritance are explained.
8. Are mutations and pedigree analysis covered? Yes, gene vs chromosomal mutations and pedigree symbols/interpretation are included.
9. Are chromosomal disorders given with examples? Yes, Down’s, Turner’s, and Klinefelter’s syndromes are briefly explained.
10. Are these notes useful for NEET? Absolutely—high-yield NCERT points, tables, and ratios (3:1, 9:3:3:1) are highlighted for NEET.