Xam Idea Class 12 Biology Chapter 5 Solutions: Principles Of Inheritance & Variation

Xam Idea Class 12 Biology Solutions for Chapter 5 ‘Principles Of Inheritance & Variation’ are deemed the best tool you can take in use to strengthen the Biology Part for board exams. Use our solutions for this chapter to understand every single thing about hereditary characteristics in humans. You will study the laws of inheritance, that tells you cross-linkage about tall and dwarf plants. You will also learn about linkage and assortment, sex determination in humans, mutation, etc. Further, you will get to learn about Mendelian disorders and chromosomal disorders. After studying this chapter from our Xam Idea solutions, you can easily grasp the answer technique that helps you fetch extra marks in the CBSE exams.

Principles Of Inheritance & Variation Solutions of Xam Idea Class 12 Biology textbook are summed up with the 224 questions. The questions are segregated into three sections Very Short Questions, Short Questions Type I & II, and Long Answer Questions, respectively. With proper practise of these questions, all your concepts associated with Principles Of Inheritance & Variation will be crystal clear. You will answer questions on genes, allele, inheritance patterns, dominance and codominance in human populations. Also, some questions are based on test cross and dihybrid cross.

Instasolv is an excellent resource to prepare the Xam Idea Class 12 Biology Chapter 5 Principles Of Inheritance & Variation for your upcoming CBSE exams. We have provided you with a clear description of the Xam Idea questions. The solutions are designed as per the latest CBSE Class 12 guidelines. Our Xam Idea solutions for Class 12 biology have been plotted after extensive research by our subject experts and will also be helpful for you to perform well at prestigious examinations like NEET.

Important Topics of Xam Idea Class 12 Biology Solutions Chapter 5: Principles Of Inheritance & Variation

Let’s be familiar with the important concepts associated with Principles Of Inheritance & Variation.

Mendel’s Law of Inheritance

Mendel did his experiments on Pisum Sativum garden pea plants to study the inheritance pattern, let’s see what he found through these experiments.

In his experiments, he followed the 7 traits of inheritance in pea plants, each with two forms, what he identified in it, that pure breeding plants show 1 type of trait after generation of pollination.

He then crossed the tall and dwarf plants to study the interference pattern in pea plants, he found that all the hybrids in the first generation F1 were the same as one parent.

Like, when all the purple progeny’s crosses with the white flower, were purple. However, when he made them in self-pollination, all the hidden traits and characteristics of hybrids would reappear in the second generation F2.

He proposed two laws based observations in monohybrid cross, that will be called as a principle of Inheritance-

  • Law of Dominance.
  • Law of Segregation.

Linkage And Recombination

You know that some traits are not compelled with Mendel’s law of independent assortment, that’s why genetic linkage is done to inherit with the segments of a chromosome. It’s nothing, a tendency of genes to be linked as a group on the chromosomes.

Recombination is the process of separating the genes during the crossing over.


The Mutation is an alteration seen in the DNA sequences. Changes could happen due to mistakes in the copying of DNA sequences or through environment such as UV light, smoking a cigarette.

Typically we have four types of mutation. Let’s have to see them-

  • Substitution
  • Insertion 
  • Deletion
  • Frameshift

Mendelian Disorders

Here we have enlisted some Mendelian disorders, have a look at them-

  • Cystic fibrosis
  • Sickle-cell anaemia
  • Color-Blindness
  • Phenylketonuria
  • Thalassemia
  • Haemophilia

Gene Therapy

Simply, you can say that it’s a technique that is used to treat human diseases by introducing DNA sequences. In this, a new DNA has been introduced, possessing a functional gene to prevent the patients from diseases that cause Mutation.

Typically it is of two types-

  • Somatic Gene therapy-  In this, a section of DNA is introduced to the cell that does not produce sperms or eggs. The traits will not pass to the producing species in future generations.
  • Germline Gene Therapy- In this therapy, a section of DNA has been transferred to that cell, that produces sperms or eggs. The traits and hereditary characteristics will be passed to the children and future generations.

Exercise Discussion of Xam Idea Class 12 Biology Solutions Chapter 5: Principles Of Inheritance & Variation.

Xam Idea Class 12 Biology Solutions Principles Of Inheritance & Variation solutions include 224 questions covering each and every aspect of Inheritance and Variation. They are divided into 4 kinds of exercises each having two different parts PYQ (past years questions) and OIQ (objective inventory questionnaires).

Very Short Answer Type Questions

  • You will have 76 questions in this section. 32 in the PYQ part and 44 in the OIQ part, generally a one-liner type, simple to counter, will give you a brief overview of the concepts involved in it.
  • In the PYQ part, you will have questions on gene and allele, on homogeneous, heterogeneous population in a typical monohybrid cross.
  • You will find three questions on guardian plea plants. You need to identify the dominant traits in it.
  • While, in the OIQ part, you will be asked to identify the sex-linked and autosomal traits, also need to give an example of chromosomal disorders caused due to non-disjunction of autosomes.
  • Also, you will have questions on pedigree charts, on point mutation, polyploidy, aneuploidy, and so on.

Short Answer Questions Type – I

  • Short Answer Type I, has 71 questions in total. You will find 44 questions in the PYQ part whereas 27 in the OIQ part.
  • In this question, you will have questions on test cross, on Pleiotropy, and Male & Female heterogeneity. You need to describe them with an example.
  • You will be asked to find the percentage of homogeneous & heterogeneous individuals in a cross between true-breeding plants and green pods with the help of Punnett square.
  • Also, we will have questions based on the phenomenon of dominance, codominance, and multiple alleles in the human population.
  • In the OIQ part, you will have questions on Blood group relations, at which you need to justify the Inheritance pattern with the help of Punnett square and cross diagrams. Also, In one of the questions, you will be asked to define trisomy with an example.

Short Answer Questions Type – II

  • Here, you will be asked to solve 29 questions. The PYQ part comprises 18 odd questions while the OIQ part has 11 questions.
  • You will have questions on mendelian Disorders like Sickle-cell Anaemia, Hemophilia. All you need to do in it, to write the Symptoms of them.
  • There is one question of type, at which you will see that snapdragon shows incomplete dominance for flower colour. In it, you just need to work out across and explain the phenomenon of it, and to describe how it’s different from the Mendelian pattern.

Long Answer Type Questions

  • This section gives you 48 around solutions for Xam Idea Class 12 Biology Principles of Inheritance & Variation. These questions will give you an in-depth understanding of the concepts associated with it.
  • There are 40 questions in the PYQ part and 8 questions in the OIQ part. All of them are based on the concepts that you learn in this chapter.
  • You will have questions on Mendelian Dihybrid Cross, on Independent Law Assortment, questions on linkage, Mutation, Chromosomal Disorders, and so on.
  • You will have questions on gene mapping, questions on Mendel law of segregation, on multiple recessive alleles as well.
  • In one of the questions, you need to explain the contribution of Alfred Sturtevant in chromosome mapping. 
  • All of these will develop an understanding of genes, inheritance, and variation in you. All you need to do is practice these questions.

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  • We focus on conceptual understanding and our solutions have been drafted in a manner that all your concepts regarding this chapter will be brightened.
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