Principles of Inheritance and Variation
ICSE · Class 12 · Biology
Summary of Principles of Inheritance and Variation for ICSE Class 12 Biology. Key concepts, important points, and chapter overview.
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Genetics is the study of heredity and variation. Heredity means transmission of genetically based characters from parents to offspring, while variation means differences among offspring and parents or among individuals of the same species. Gregor Johann Mendel laid the foundation of inheritance stud
Key Concepts
Heredity is the transmission of traits
Heredity is the transmission of traits from one generation to the next. Variation is the difference seen among individuals, even within the same famil
Mendel's work on garden pea led
Mendel's work on garden pea led to three main ideas used in inheritance studies: law of dominance, law of segregation, and law of independent assortme
A monohybrid cross involves one pair
A monohybrid cross involves one pair of contrasting characters and gives F2 phenotypic ratio 3 : 1 and genotypic ratio 1 : 2 : 1. A dihybrid cross inv
Incomplete dominance appears when neither allele
Incomplete dominance appears when neither allele is completely dominant. The F1 hybrid shows an intermediate phenotype. Snapdragon and four O'clock pl
Codominance occurs when both alleles express
Codominance occurs when both alleles express themselves equally in a heterozygote. Roan coat colour in cattle is a classic example. The ABO blood grou
Learning Objectives
- Understand heredity, variation, genotype, phenotype, homozygous and heterozygous conditions
- Explain Mendel's laws of dominance, segregation, and independent assortment
- Interpret monohybrid, dihybrid, and trihybrid ratios
- Describe incomplete dominance, codominance, pleiotropy, and multiple alleles
- Explain the chromosomal theory of inheritance and linkage
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