Chapter 4 of 10
Revision Notes
Principles of Inheritance and Variation — Revision Notes
Tamil Nadu Board · Class 12 · Zoology
Principles of Inheritance and Variation revision notes for Tamil Nadu Board Class 12 Zoology: 4 topics in quick points.
44 questions24 flashcards5 concepts
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Key Topics to Revise
1
4.1 Multiple Alleles
- A gene can exist in multiple forms called alleles
- When three or more alleles of a gene occupy the same locus on homologous chromosomes, it is called multiple alleles
- Inheritance involving multiple alleles is called multiple allelism
2
4.2 Human Blood Groups - ABO System
- Blood group inheritance is a classic example of multiple allelism in humans
- Karl Landsteiner discovered antigens A and B on red blood cell surfaces
- Three alleles control ABO blood groups: I^A, I^B, and I^O
3
4.3 Genetic Control of Rh Factor
- Rh factor (Rh antigen/D antigen) discovered in 1940 in rhesus monkey blood
- Present on red blood cell surfaces like ABO antigens
- Individuals with D antigen are Rh positive (Rh⁺); those without are Rh negative (Rh⁻)
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4.3.1 Erythroblastosis Foetalis (Hemolytic Disease of Newborn)
- Occurs when Rh negative mother carries Rh positive fetus
- Mother becomes sensitized during pregnancy or childbirth when fetal blood enters maternal circulation
- Maternal immune system produces anti-D antibodies (IgG type)
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Full NotesKey Concepts
Multiple alleles occur when a geneThe ABO blood group is determinedThe Rh factor is a DSex determination varies across speciesFemales have two X chromosomes while
Frequently Asked Questions
What are the important topics in Principles of Inheritance and Variation for Tamil Nadu Board Class 12 Zoology?
Key topics in Principles of Inheritance and Variation include 1 Multiple Alleles, 2 Human Blood Groups - ABO System, 3 Genetic Control of Rh Factor, 3.1 Erythroblastosis Foetalis (Hemolytic Disease of Newborn). Study these first, then practise questions on each for the Tamil Nadu Board Class 12 board exam.
How should I revise Principles of Inheritance and Variation for the Tamil Nadu Board Class 12 board exam?
Learn the core ideas first, then work through the 44 practice questions on Principles of Inheritance and Variation. Revise definitions regularly and use flashcards for quick recall before the exam.
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