You will get here Science Biology class 12 CBSE notes Chapter 4: Principles of Inheritance and Variation. You can connect with us for every important update related to class 12.
Science Biology is a very important subject for you because it will help you increase your percentage as well as it is an important subject for your medical entrance exam. You can score high marks in this subject by studying notes and practicing MCQs. In this post, we will cover Chapter 4: Principles of Inheritance and Variation.
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Key Content Of Chapter 4 Principles of Inheritance and Variation
🧬 What is Inheritance and Variation?
- Inheritance → Passing of traits from parents to offspring
- Variation → Differences in traits among individuals
- Controlled by genes, which are present on chromosomes
👨🔬 Mendel and His Experiments
- Gregor Mendel is known as the Father of Genetics
- He performed experiments on pea plants (Pisum sativum)
- Traits studied: height, flower colour, seed shape, etc.
🌱 Important Genetic Terms
- Gene → unit of heredity
- Allele → alternative form of a gene
- Genotype → genetic makeup (TT, Tt, tt)
- Phenotype → physical appearance (tall, short)
- Homozygous → same alleles (TT or tt)
- Heterozygous → different alleles (Tt)
🌿 Mendel’s Laws of Inheritance
1. Law of Dominance
- One allele expresses itself (dominant)
- Other gets masked (recessive)
2. Law of Segregation
- Alleles separate during gamete formation
- Each gamete gets only one allele
3. Law of Independent Assortment
- Genes for different traits assort independently
🌸 Monohybrid Cross
- Cross involving one trait
- Example: Tall (TT) × Short (tt)
- F1 generation → all Tall (Tt)
- F2 ratio → 3:1 (Phenotype)
🌼 Dihybrid Cross
- Cross involving two traits
- Example: Seed shape & colour
- F2 ratio → 9:3:3:1
⚡ Extensions of Mendelism
- Incomplete Dominance → no allele is fully dominant (Pink flower)
- Codominance → both alleles express (AB blood group)
- Multiple Alleles → more than two alleles (ABO blood group)
🧬 Chromosomal Theory of Inheritance
- Proposed by Sutton & Boveri
- Genes are located on chromosomes
- Explains Mendel’s laws
🧪 Linkage and Recombination
- Linkage → genes present on same chromosome inherited together
- Recombination → exchange of genes during crossing over
👦 Sex Determination
- Humans follow XX-XY system
- Male → XY
- Female → XX
- Father determines the sex of child
🧬 Mutation
- Sudden change in genetic material
- Leads to variation
- Can be harmful or beneficial
🌟 Genetic Disorders
- Mendelian Disorders → due to single gene
- Example: Haemophilia, Sickle cell anaemia
- Chromosomal Disorders → due to chromosome abnormality
- Example: Down syndrome
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Class 12 Science Biology Chapter 4: Principles of Inheritance and Variation Notes
Principles of Inheritance and Variation
Class 12 Biology Chapter 4 – Pulse by Anubhav
Complete notes, NCERT-based content aur updated syllabus yahan se easily access karo.
Yeh chapter Mendel’s laws, inheritance patterns, genetic variation, linkage aur human genetic disorders ko simple way me explain karta hai — boards aur NEET ke liye highly important 🔥
Class 12 Biology Chapter 4 Principles of Inheritance and Variation MCQs
Principles of Inheritance and Variation (MCQs) – Pulse by Anubhav
1. Who is known as the Father of Genetics?
A. Darwin
B. Gregor Mendel
C. Lamarck
D. Watson
2. Unit of heredity is:
A. Cell
B. Gene
C. Tissue
D. Organ
3. Alternative forms of a gene are called:
A. Chromosomes
B. Alleles
C. Cells
D. Traits
4. Phenotypic ratio of monohybrid cross is:
A. 1:1
B. 3:1
C. 9:3:3:1
D. 2:1
5. Phenotypic ratio of dihybrid cross is:
A. 3:1
B. 9:3:3:1
C. 1:1
D. 2:1
6. Law of segregation states:
A. Traits mix together
B. Alleles separate during gamete formation
C. Genes disappear
D. Traits are lost
7. Incomplete dominance results in:
A. Dominant phenotype only
B. Intermediate phenotype
C. No phenotype
D. Mutation
8. Chromosomal theory of inheritance was proposed by:
A. Mendel
B. Sutton and Boveri
C. Darwin
D. Morgan
9. Human males have which chromosomes?
A. XX
B. XY
C. YY
D. XO
10. Down syndrome is an example of:
A. Mendelian disorder
B. Chromosomal disorder
C. Mutation only
D. Infection
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FAQs About Principles of Inheritance and Variation
Principles of Inheritance and Variation – FAQs (Pulse by Anubhav)
1. What is inheritance in biology?
Inheritance is the process by which traits are passed from parents to offspring through genes.
2. Who is the Father of Genetics?
Gregor Mendel is known as the Father of Genetics.
3. What is a gene?
A gene is the basic unit of heredity that controls specific traits.
4. What is the phenotypic ratio of a monohybrid cross?
The phenotypic ratio of a monohybrid cross is 3:1.
5. What is variation?
Variation refers to the differences in traits among individuals of the same species.
6. What is Mendel’s Law of Segregation?
It states that allele pairs separate during gamete formation, and each gamete carries only one allele.
7. What is codominance?
Codominance is when both alleles express equally in an organism, such as AB blood group.
8. What is a chromosomal disorder?
A disorder caused by abnormal number or structure of chromosomes, like Down syndrome.
Class 12 Biology Notes – All Chapters (Pulse by Anubhav)
| Chapter | Topic | Open |
|---|---|---|
| Chapter I | Sexual Reproduction in Flowering Plants | View → |
| Chapter II | Human Reproduction | View → |
| Chapter III | Reproductive Health | View → |
| Chapter IV | Principles of Inheritance and Variation | View → |
| Chapter V | Molecular Basis of Inheritance | View → |
| Chapter VI | Evolution | View → |
| Chapter VII | Human Health and Disease | View → |
| Chapter VIII | Microbes in Human Welfare | View → |
| Chapter IX | Biotechnology: Principles and Processes | View → |
| Chapter X | Biotechnology and its Applications | View → |
| Chapter XI | Organisms and Populations | View |
| Chapter XII | Ecosystem | View → |
| Chapter XIII | Biodiversity And Conservation | View → |