NCERT Solutions For Class 12 Biology Chapter 5: Principles of Inheritance and Variation

NCERT Solutions for Class 12 Biology Chapter 5 Principles of Inheritance and Variation are provided in this article. It includes all the important definitions, concepts, and methodologies that will be beneficial for the students appearing for the CBSE Class 12 Exam 2024-25. Students can easily access the NCERT Solutions for class 12 by clicking on the download link below. The important topics that are included in this chapter are:

• Mendelian Inheritance
• Chromosomal Theory of Inheritance
• Sex Determination
• Linkage and crossing over
• Mutation 
• Genetic Disorders

Expected no. of Questions: 3-4 questions of around 6 marks.

Download PDF: NCERT Solutions for Class 12 Biology Chapter 5 Principles of Inheritance and Variation

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NCERT Solutions for Class 12 Biology Chapter 5

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Class 12 Biology Chapter 5 Principles of Inheritance and Variations: Important Topics

The Principle of Inheritance and Variation class 12 explains the study of heredity and variation principles along with their mechanism. Inheritance explains how characteristics are passed on from one generation to the next and that variation may depend on factors such as physical, mental, emotional, and behavioral. The important topics that are covered in this chapter are discussed below:

Mendelian Inheritance 

Mendelian inheritance is defined as certain patterns of how traits or characteristics are passed from parents to offspring. Austrian monk Gregor Mendel was the first person to establish these general patterns by performing thousands of experiments with pea plants in the 19th century.

Read more: CBSE Class 12 Biology Chapter 5 notes

Chromosomal Theory of Inheritance

The chromosomal theory of inheritance, which was given by Boveri and Sutton in the early 1900s, is the fundamental theory of genetics.

• This theory states that genes are the units of heredity and are found in the chromosomes. 
• Experiments were performed on fruit flies and Drosophila Melanogaster. 

Sex Determination

The system used to determine whether an individual is a male or female is called sex determination.

• Chromosomes used to identify the sex of the child are called sex chromosomes. 
• When males produce two different gametes, it is called male heterogamety.
• Female heterogamety means when a female produces two different gametes. 

Read more: Principle of Inheritance Important Questions

Genetic Disorders

The disorders which occur due to mutation in genes are called genetic disorders. The risk of such type of disorders is determined using pedigree charts or analysis. It is a study carried out to determine a disease by studying the inheritance pattern of the family. Mendelian and Chromosomal disorders are the two types of genetic disorders.

Mendelian Disorders

The disorders that affect one gene or result in mutations in the genome are called Mendelian disorders.

• Colorblindness: Colourblindness is a disorder caused by mutation of genes present on the X chromosome. A person fails to see certain colours like red, blue, and green.
• Hemophilia: In this disease, a protein responsible for clotting blood is affected. A person’s body fails to clot blood. 

Chromosomal Disorders

Any change in the chromosome of an individual is called a chromosomal disorder.

• Down Syndrome is a condition wherein a person has an extra 21^st chromosome.
• Kleinfelters syndrome is a type of syndrome wherein a person has an extra X chromosome resulting in 47 chromosomes.
• Turners syndrome results in the absence of an X chromosome ie; there are 45 chromosomes present in total.

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