logo
Log in
  Get Rs 200 off on Oswal Premium Plan this New Year! For Class 9th and 12th. Use Coupon Code NEWYEAR200 at checkout.
logo
Log in
Start Free Trial
Principles of Inheritance and Variation

Home / Boards / CBSE / Important Questions / Class 12 / Biology / Principles of Inheritance and Variation

Class 12 Biology Chapter 4
Principles of Inheritance and Variation
Important Questions

exam preparation with oswal.io
Explore crucial questions related to Chapter 4 on Principles of Inheritance and Variation for Class 12 Biology. These specific queries have been crafted to assist students in preparing for the CBSE Class 12 Biology Examination 2024–25. Engaging with various question formats will enable students to address uncertainties, ensuring thorough readiness for the upcoming exams. Tackling these questions not only boosts confidence but also hones problem-solving skills. Elevate your understanding of sexual reproduction in flowering plants with these essential Class 12 Biology questions, covering both the vital and most important aspects of the topic.

Introduction

Principles of Inheritance and Variation form a pivotal chapter in Class 12 Biology, unravelling the genetic intricacies that dictate the transmission of traits from one generation to the next. This exploration delves into the fundamental principles that govern heredity and the diversity observed within a species. From Mendel’s laws to the complexities of gene expression, the chapter elucidates the mechanisms underlying inheritance and the factors contributing to genetic variation. As we navigate this genetic landscape, students are encouraged to engage with Principles of Inheritance and Variation class 12 important questions, thereby fortifying their understanding and preparation for the CBSE Class 12 Biology Examination 2024–25.

What are Principles of Inheritance and Variation?

Principles of Inheritance and Variation encapsulate the fundamental rules governing the transmission of genetic material from parent to offspring and the factors influencing the diversity observed within a population. This chapter explores the foundational work of Gregor Mendel, who laid the groundwork for understanding heredity through his experiments with pea plants. The principles encompass the laws of segregation and independent assortment, shedding light on the patterns through which traits are inherited. Additionally, the chapter delves into the intricacies of variations arising from genetic and environmental factors, providing a comprehensive understanding of the mechanisms shaping the genetic makeup of individuals.

Class 12 Principles of Inheritance and Variation Important Questions and Answers

Q1. In a dihybrid cross, if the two alleles of a gene sort independently of the alleles of another gene, it is an example of:
Options
(a) Law of Dominance
(b) Law of Independent Assortment
(c) Law of Segregation
(d) Incomplete Dominance

Ans. (b) Law of Independent Assortment
Explanation:
The Law of Independent Assortment states that alleles of different genes segregate independently during the formation of gametes. This principle is observed in dihybrid crosses when traits are controlled by different genes located on separate chromosomes. This law allows for the prediction of genetic variation in offspring.

Q2. Which of the following is not a Mendelian disorder?
Options
(a) Haemophilia
(b) Down syndrome
(c) Cystic fibrosis
(d) Sickle cell anaemia

Ans. (b) Down syndrome
Explanation:
Down syndrome is a chromosomal disorder caused by the presence of an extra chromosome 21 (trisomy 21). In contrast, Haemophilia, cystic fibrosis, and sickle cell anaemia are Mendelian disorders caused by mutations in single genes, following Mendelian inheritance patterns.

Q3. What is Co-dominance? Give an example.

Explanation:
Co-dominance occurs when both the alleles of a gene in a heterozygote are fully expressed, leading to a phenotype that showcases both traits without one being dominant over the other.
Example: An example of codominance is the AB blood group in humans. In this case, both the A and B alleles are expressed equally, resulting in an individual with type AB blood, which exhibits characteristics of both A and B blood types.

Q4. Explain the concept of pleiotropy with an example.

Explanation:
Pleiotropy refers to a genetic phenomenon where a single gene influences multiple phenotypic traits in an organism. This means that mutations or variations in that gene can lead to several different effects.
Example
A classic example of pleiotropy is the gene responsible for sickle cell anaemia. This gene alters the structure of haemoglobin, resulting in the formation of sickle-shaped red blood cells. The effects of this gene include:

  • Anaemia: Due to the destruction of the misshapen red blood cells.
  • Pain episodes: Caused by the blockage of blood flow in small blood vessels.
  • Increased susceptibility to infections: Due to compromised spleen function.
Q5. Discuss the genetic basis of sex determination in humans.

Explanation:
In humans, sex determination is based on the XY chromosome system. The genetic basis involves two sex chromosomes, X and Y. Females have two X chromosomes (XX), while males have one X and one Y chromosome (XY).

  • The presence of the Y chromosome is critical for male development. The Y chromosome contains the SRY gene (Sex-determining Region Y), which triggers male sex determination. The SRY gene codes for a protein that initiates the development of testes, the male reproductive organ.
  • In the absence of a Y chromosome (as in XX females), the default developmental pathway leads to the formation of ovaries, the female reproductive organ.
    Besides the presence of the SRY gene, other genes on both the X and Y chromosomes are involved in sex determination and differentiation.
  • The X chromosome carries genes that are essential for both sexes. Since males have only one X chromosome, any recessive trait on the X chromosome will be expressed in males, a phenomenon known as X-linked inheritance. This is why disorders like haemophilia and colour blindness are more common in males.
  • The ratio of X chromosomes to sets of autosomes (X:A ratio) also plays a role in determining the sex, especially in some insects.

This genetic mechanism of sex determination emphasises the role of chromosomes and specific genes in the development of sexual characteristics in humans.

CBSE Class 12 Biology Chapter wise Important Questions

Chapter No.Chapter Name
Chapter 1Sexual Reproduction in Flowering Plants
Chapter 2Human Reproduction
Chapter 3Reproductive Health
Chapter 4Principles of Inheritance and Variation
Chapter 5Molecular Basis of Inheritance
Chapter 6Evolution
Chapter 7Human Health and Disease
Chapter 8Microbes in Human Welfare
Chapter 9Biotechnology: Principles and Processes
Chapter 10Biotechnology and its Applications
Chapter 11Organisms and Populations
Chapter 12Ecosystem
Chapter 13Biodiversity and Conservation

Conclusion

Principles of Inheritance and Variation navigates the principles laid down by Mendel, exploring how traits are inherited and the factors contributing to genetic diversity. To enhance your mastery of this topic, engage with Principles of Inheritance and Variation class 12 important questions, meticulously designed to fortify your knowledge and readiness for the CBSE Class 12 Biology Examination 2024–25. Oswal.io,provides a rich collection of questions and materials.

Frequently Asked Questions

Ans: Mendel’s Laws of Inheritance consist of the Law of Segregation, stating that alleles segregate during gamete formation, and the Law of Independent Assortment, stating that alleles of different genes segregate independently. These laws laid the foundation for understanding the patterns of inheritance.
Ans: In complete dominance, one allele completely masks the effect of the other in a heterozygous individual, resulting in a distinct phenotype. In incomplete dominance, neither allele dominates, leading to an intermediate phenotype that is a blend of the two alleles.
Ans: Punnett squares are a visual tool used to predict the possible genotypes of offspring in a genetic cross. They help determine the probability of specific trait combinations based on the alleles carried by the parent organisms.
Ans: Multiple alleles refer to the existence of more than two alleles for a particular gene in a population. The presence of multiple alleles, along with various combinations, leads to a diverse range of phenotypic expressions for a specific trait, contributing to genetic diversity.
Ans: Environmental factors, such as nutrition, temperature, and exposure to substances, can influence the expression of traits in individuals. While genes provide the blueprint for traits, the interaction between genes and the environment contributes to the variations observed within a population.
Chapter Wise Important Questions for CBSE Board Class 12 Biology
Sexual Reproduction in Flowering Plants
Human Reproduction
Reproductive Health
Principles of Inheritance and Variation
Molecular Basis of Inheritance
Evolution
Human Health and Disease
Microbes in Human Welfare
Biotechnology: Principles and Processes
Biotechnology and its Applications
Organisms and Populations
Ecosystem
Biodiversity and Conservation
logo
Instagram Linkedin-in Facebook-f Youtube Twitter
logo
Instagram Linkedin-in Facebook-f Youtube Twitter

CBSE Important Questions Class 10

ICSE Important Questions Class 10

CBSE Important Questions Class 10

ICSE Important Questions Class 10

Contact Us

© Copyright 2024 oswal.io by OSWAL PUBLISHERS Simplifying Exams