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Ncert Solutions For Class 12 Biology Chapter 5 Download PDFs

Class 12 Biology ch 5 NCERT Solutions: Adda 247 provides NCERT Solutions for Class 12 Biology Chapter 5 which is for the students who want to go ahead in life and achieve great marks in their examinations. The NCERT Solutions for class 12 are provided by the teachers who are experts of their subjects. The solutions are set according to the rules formulated by the NCERT class 12 biology and in the language that can be understood by every student. By these reading the solutions students can build up a strong base easily. The NCERT class 12 Biology solutions covers the chapters 1 to 16 with the important questions and the answers in a detailed way.

Examinations can be threatening for some people, a proper learning of the concepts is the key to crack the examination. Students rely on the solutions of the NCERT provided by Adda 247. The solutions are formulated by the experts of the subjects who have tremendous knowledge in their subjects.

These NCERT Solutions of class 12 help the students to get familiarized with the textbooks. The students can access the solutions anywhere while browsing the web easily. The solutions are very precise and accurate.


NCERT Solutions for Class 12 Biology Chapter 5 – Principles of Inheritance and variation 

The chapter provides information about Principles of Inheritance and Variation. Heredity is the transfer of character from parents to their offspring. These hereditary characters are present on the chromosomes in the form of genes.  These gene combinations express characters which may be more similar to one of its two parents. The differences in characters of offspring mainly depend upon unique process of crossing over that occurs during meiosis.  This is one of the main reasons of producing recombination.

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Features of the NCERT Solutions of Class 12 Biology Chapter 5 – Principles of Inheritance and variation


NCERT Solutions of class 12 have been answered based on the important information on the question.

  • The columns are used wherever necessary.
  • Solutions are solved point wise and accurately answered point to point.


Important Questions of Ncert Solutions for Class 12 Biology Chapter 5


Question 1. Mention the advantages of selecting pea plant for experiment by Mendel.


Answer:  The advantages of selecting garden pea (Pisum sativum) for experiments by Mendel were –

  1. Pea has many visibly distinct contrasting characters.
  2. The life span of the pea plant is short and they produce many seeds in one generation.
  3. Pea flowers are bisexual and show self-pollination, reproductive whorls being enclosed by corolla.
  4. It is easy to artificially cross-pollinate the pea flowers. The hybrids thus produced were fertile.


Question 2.  Differentiate between the following –

(a) Dominance and Recessive

(b) Homozygous and Heterozygous

(c) Monohybrid and Dihybrid.

Answer:  (a) Dominance and Recessive

Dominance Recessive
A dominant factor or allele expresses itself in the presence or absence of a recessive factor. A recessive trait is able to express itself only in the absence of a dominant factor.
For example, tall plant, round seed, violet flower, etc. are dominant traits in a pea plant. For example, dwarf plant, wrinkled seed, white flower, etc. are recessive traits in a pea plant.


(b) Homozygous and Heterozygous

Homozygous Heterozygous
It contains two similar alleles for a particular trait. It contains two different alleles for a particular trait.
Genotype for homozygous possess either dominant or recessive, but never both the alleles. For example, RR or rr  


Genotype for heterozygous possess both dominant and recessive alleles. For example, Rr

It produces only one type of gamete. It produces two different kinds of gametes.


(c) Monohybrid and Dihybrid

Monohybrid Cross Dihybrid Cross
Monohybrid Cross involves cross between parents, which differs in only one pair of contrasting characters. Dihybrid Cross involves cross between parents, which differs in two pairs of contrasting characters.
For example, the cross between tall and dwarf pea plant is a monohybrid cross. For example, the cross between pea plants having yellow wrinkled seed with those having green round seeds is a dihybrid cross.


Question 3. A diploid organism is heterozygous for 4 loci, how many types of gametes can be produced?


Answer: Locus is a fixed position on a chromosome, which is occupied by a single or more genes. Heterozygous organisms contain different alleles for an allelic pair. Hence, a diploid organism, which is heterozygous at four loci, will have four different contrasting characters at four different loci. For example, if an organism is heterozygous at four loci with four characters, say Aa, Bb, Cc, Dd, then during meiosis, it will segregate to form 8 separate gametes.

Types of gametes produced by organism=  wherein n= number of loci for which the organism is heterozygous. The given diploid organism is heterozygous for 4 loci, types of gametes produced =  = 16.


Question 4. Explain the Law of Dominance using a monohybrid cross.


Answer:  Mendels law of dominance states that a dominant allele expresses itself in a monohybrid cross and suppresses the expression of recessive allele. However, this recessive allele for a character is not lost and remains hidden or masked in the progenies of F1generation and reappears in the next generation.

For example, when pea plants with round seeds (RR) are crossed with plants with wrinkled seeds (rr), all seeds in F1 generation were found to be round (Rr). When these round seeds were self-fertilized, both the round and wrinkled seeds appeared in F2 generation in 3: 1 ratio. Hence, in F1 generation, the dominant character (round seeds) appeared and the recessive character (wrinkled seeds) got suppressed, which reappeared in F2 generation.


Question 5. Define and design a test-cross.


Answer:  Test cross is a cross between an organism with unknown genotype and a recessive parent. It is used to determine whether an individual is homozygous or heterozygous for a trait.


Suppose you have a violet and white flower and violet color (P) is dominant to white (p). The white flower must be homozygous for the recessive allele, but the genotype of the violet flower is unknown. It could be either PP or Pp.

A testcross will determine the organism’s genotype. The unknown genotype can be determined by observing the phenotypes of the resulting offspring.

If crossing the unknown dominant phenotype (PP or Pp genotype) individual with the recessive phenotype individual produces only dominant phenotypes (no recessive), then the unknown individual is homozygous dominant.

If any recessive phenotypic individuals result from the cross, then the unknown individual must carry the recessive allele, and have the heterozygous genotype.


Question 6. Using a Punnett Square, workout the distribution of phenotypic features in the first filial generation after a cross between a homozygous female and a heterozygous male for a single locus.


Answer:  The phenotypic features in the first filial generation after a cross between a homozygous female and a heterozygous male for a single locus, say height, is as follows:


Question 7.  When a cross in made between tall plant with yellow seeds (TtYy) and tall plant with green seed (Ttyy), what proportions of phenotype in the offspring could be expected to be

(a) tall and green.

(b) dwarf and green.


Answer:  As given phenotype of TtYy parent, tallness is dominant over dwarfism and yellow seed is dominant over green seeds. Genotype of tall and green progeny will be Ttyy and TTyy, and that of dwarf and green progeny will be ttyy. Proportion of tall and green progeny= 3

Proportion of dwarf and green progeny= 1


Question 8. Two heterozygous parents are crossed. If the two loci are linked what would be the distribution of phenotypic features in F1 generation for a dihybrid cross?


Answer:  In this case, the distribution of phenotypic feature would follow the same pattern as in dihybrid cross done by Mendel. It is important to recall the Law of Independent Assortment while answering this question. This law says that different traits segregate independent of each other; during gamete formation.


Question 9. Briefly mention the contribution of T.H. Morgan in genetics.


Answer:  The contributions of T.H. Morgan are:

  1. Morgan was the first to provide experimental verification for the chromosomal theory of inheritance by his work on Drosophila melanogaster.
  2. He defined linkage between two genes located close together which are always inherited together.
  3. The identified linkage to be of two types tightly linked genes, where both the genes are passed onto the next generation and loosely linked genes in which recombination may take place due to a large distance present within the two genes.
  4. He also defined the term recombination of non – parental gene recombination.
  5. His findings of linked genes pavemented the path for genome mapping that is done today.
  6. He also contributed to the understanding of sex – linked inheritance vii. He has also worked on mutations.


Question 10. How is sex determined in human beings?


Answer: Sex determination in human beings

In humans, out of 23 pairs of chromosomes, 22 pairs are exactly the same in male and female called autosomes. However, a pair of the X chromosome is present in female and XY in male. During spermatogenesis, male produce two types of gametes (sperms), 50% carries Y chromosome and remaining 50% contain X chromosome. On the other hand, female produces only one kind of gamete (ovum) having X chromosomes only. When sperm having Y chromosome fertilises the ovum the sex of the baby is male and when sperm carrying X chromosome fertilises the egg, the sex of the baby is female.


Frequently Asked Questions on NCERT Solutions for Class 12 Biology Chapter 5


What are the advantages of referring NCERT Solutions for class 12 Biology chapter 5?

Students referring the NCERT Solutions of class 12 by Adda 247 find the solutions helpful during the exams. The solutions are prepared by the experts in an interactive manner keeping in mind the students. The students’ perspective is kept in mind while preparing the solutions. It helps in completing the syllabus on time and also provides notes for the revision prior to the exam.


What are the advantages of referring NCERT in competitive exams like JEE and AIPMT?

Most of the competitive exams like NEET, JEE etc. follow the basic NCERT books for designing their question papers. NCERT serves as the base for every book prepared for NEET and JEE. The competitive exams are based on the CBSE syllabus applied in XI and XII classes and NCERT books strictly follow CBSE syllabus. In addition to this, NCERT books play an important role in clearing out the theoretical concepts. Every topic given in NCERT books is explained in such a way to help students make their basics and fundamentals strong and clear.


How to read NCERT books more efficiently?

Given below are the important points which must be followed while reading the NCERT books in an efficient manner:

Go through each topic thoroughly by understanding the meaning and significance of each line mentioned in that particular topic.

Ask your teacher if any doubts.

Note down the important topics to revise at the time of examination.

Solve all the exercise questions given at the end of each chapter. These questions are important for understanding the concepts in a better way.


Is it mandatory to solve all the NCERT questions mentioned at the end of each chapter?

The questions and answers mentioned in NCERT textbooks at the end of each chapter are quite important not only for examination but also for understanding the concepts in a better way. These questions aim to test the students’ understanding and learning over the topics that they have learned in the chapter.

Solving the NCERT exercise problems will help to

  • clear all the concepts and formulae you learned in a chapter
  • get comfortable with different types of questions that might be asked in exams
  • get enough practice which is key to succeed in Mathematics exam
  • improve your accuracy and speed


What are the important concepts covered in the Chapter 5 of NCERT Solutions for Class 12 Biology?

The concepts involved in chapter 5 of NCERT Solutions are –

5.1 – Mendel’s Laws of Inheritance
5.2 -Inheritance of One Gene
5.3- Inheritance of Two Genes
5.4 – Sex Determination
5.5 – Mutation
5.6 – Genetic Disorders

These concepts are created by the faculty at Adda 247. The solutions are available at Adda 247 in the PDF format which can be downloaded by the students.

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