Aakash Repeater Courses
Take Aakash iACST and get instant scholarship on coaching programs.
NCERT Solutions for Class 12 Biology Chapter 4 Principles of Inheritance and Variation
The NCERT Solutions for Class 12 Biology Chapter 4 Principles of Inheritance and Variation help students understand how traits are inherited by offspring from their parents. This chapter will include the fundamentals of genetics and heredity, which involve Mendel's laws, kinds of inheritance, sex determination, mutations, and genetic disorders. The NCERT solutions help students clarify their concepts and improve their performance in board exams as well as entrance exams, such as NEET.
This Story also Contains
- Principles of Inheritance and Variation Class 12 NCERT Solutions- PDF Download
- Get Class 12 Biology Chapter 4 Solutions (Exercise Questions)
- Approach to Solve Class 12 Biology Chapter 4 Question Answer
- Important Question from Class 12 Biology Chapter 4 Solutions
- What Extra Should Students Study Beyond the NCERT for NEET?
- NCERT Solutions for Class 12 Biology: Chapter-wise
The Chapter 4 NCERT 12th Biology solution describes important terms such as dominant and recessive genes, monohybrid and dihybrid crosses. In this article, students can find the detailed Class 12 Biology Chapter 4 Solutions. By going through these NCERT Solutions Class 12 Biology, they will be able to learn and practice questions easily that are important for exams. The explanations given in the solutions explain the concepts in a better way and help students build a strong foundation in genetics. Principles of Inheritance and Variation NCERT PDF also includes important diagrams and examples that are often asked in exams.
Also Read,
Principles of Inheritance and Variation Class 12 NCERT Solutions- PDF Download
Students can download the PDF from the link given below to make quick and easy revision before exams. All answers are explained clearly to help understand key topics. These solutions are based on the latest syllabus and are well explained in the NCERT Solutions for Class 12.
Get Class 12 Biology Chapter 4 Solutions (Exercise Questions)
This chapter explains different principles of inheritance and variation in an easy way. To make learning easier, Class 12 Biology Chapter 4 question answers are given that help students practice all important concepts. Solving these questions regularly builds a strong base and boosts confidence for exams.
Q1. Mention the advantages of selecting a pea plant for the experiment by Mendel.
Answer:
The merits of choosing a garden pea (Pisum sativum) for experimentation by Mendel are:
-
Pea possesses numerous visible contrasting characters.
-
The duration of the life of pea plants is short, and they yield numerous seeds in a single generation.
-
Pea flowers are bisexual and exhibit self-pollination, with reproductive whorls being covered by the corolla.
-
It is not difficult to artificially cross-pollinate the pea flowers. The hybrids thus obtained were fertile.
Q2. Differentiate between the following
Answer:
|
Dominance |
Recessive |
|
Expressed in the presence of an allele |
Only expressed if the dominant is absent |
|
Functional enzyme produced |
Defective or non-functional enzyme |
(b) Homozygous and Heterozygous
Answer:
|
Homozygous |
Heterozygous |
|
Identical alleles (TT) |
Different alleles (Tt) |
|
One type of gamete |
Two types of gametes |
Answer:
|
Monohybrid |
Dihybrid |
|
One trait considered |
Two traits considered |
|
Tall vs. Dwarf pea plants |
Round/Yellow vs. Wrinkled/Green seeds |
Q3. A diploid organism is heterozygous for 4 loci. How many types of gametes can be produced?
Answer:
If a diploid organism is heterozygous at 4 loci, it implies it has four genes where it possesses two distinct alleles at each of the four loci.
We calculate the number of various gametes that can be formed by the formula 2n, where n represents the number of heterozygous loci.
Here, n = 4, thus the number of gametes = 24 = 16.
Thus, 16 different varieties of gametes can be formed.
Q4. Explain the Law of Dominance using a monohybrid cross.
Answer:
The Law of Dominance, as suggested by Mendel, is:
-
Traits are determined by factors (genes) that come in pairs (alleles).
-
In a heterozygous organism, one allele (the dominant allele) suppresses the expression of the other allele (the recessive allele).
-
The recessive allele is expressed only when it is in a homozygous state.
-
A monohybrid cross illustrates this law well. For instance, cross-pollinating a homozygous tall pea plant (TT) with a homozygous dwarf pea plant (tt):
-
P Generation: Tall (TT) x Dwarf (tt)
-
F1 Generation: All the offspring are heterozygous (Tt) and tall. The tall allele (T) is dominant to the dwarf allele (t), and therefore all plants have the tall phenotype, suppressing the dwarf trait.
-
F2 Generation: If the F1 generation (Tt) is self-pollinated, the F2 generation exhibits a 3:1 phenotypic ratio (3 tall: 1 dwarf). The dwarf trait re-emerges because some plants are now homozygous recessive (tt).
-
This re-emergence of the recessive trait in the F2 generation proves that the recessive allele existed in the F1 generation but its expression was suppressed by the dominant allele.
NEET Highest Scoring Chapters & Topics
Most Scoring concepts For NEET (Based On Previous Year Analysis)
Download EBook
In this cross, it can be seen that in the F1 generation, only tall plants were seen; no plant was a dwarf. However, in the F2 generation, the F1 progeny was self-crossed, three genotypes were observed, among these, the hybrids were showing the dominant trait.
Q5. Define and design a test cross.
Answer:
A test cross is a technique used to determine whether a person exhibiting a dominant phenotype is homozygous dominant or heterozygous for a particular character.
Definition: The cross between an F1 hybrid and its homozygous recessive parent is called a test cross.
Design:
-
Choose a person showing the dominant phenotype but having an unknown genotype (e.g., a tall plant might be TT or Tt).
-
Cross this person with a homozygous recessive person (e.g., a dwarf plant with the genotype tt).
Examine the offspring:
-
If all offspring have the dominant phenotype, the mystery parent was most likely homozygous dominant (TT).
-
If the offspring have a 1:1 ratio of dominant and recessive phenotypes, the mystery parent was heterozygous (Tt).
Answer:
Let's take one locus with alleles B (black coat colour, dominant) and b (white coat colour, recessive) in guinea pigs. A cross between a homozygous recessive female (bb) and a heterozygous male (Bb):
|
B |
b | |
|
b |
Bb |
bb |
|
b |
Bb |
bb |
-
Genotypes: 50% Bb (heterozygous), 50% bb (homozygous recessive)
-
Phenotypes: 50% black coat colour, 50% white coat colour
-
Ratio: The F1 progeny will show a 1:1 ratio of black coat colour to white coat colour.
Q7. When a cross is made between a tall plant with yellow seeds (TtYy) and a tall plant with green seeds (Ttyy), what proportions of phenotype in the offspring could be expected to be
Answer:
Let's perform the cross: TtYy x Ttyy
|
TY |
Ty |
tY |
ty | |
|
Ty |
TTYy |
TTyy |
TtYy |
Ttyy |
|
ty |
TtYy |
Ttyy |
ttYy |
ttyy |
From the Punnett square, we can determine the offspring phenotypes:
-
Tall and Yellow (T_Y_): TTYy, TtYy, TtYy (3)
-
Tall and green (T_yy): TTyy, Ttyy, Ttyy (3)
-
Dwarf and Yellow (ttYy): ttYy (1)
-
Dwarf and Green (ttyy): ttyy (1)
-
The genotypic ratio is 3:3:1:1
Hence, there will be plants showing three tall and green seed traits.
Answer:
(a) tall and green.
The proportion of tall and green offspring is 3/8 or 37.5%
(b) dwarf and green.
The proportion of dwarf and green offspring is 1/8 or 12.5%
Answer:
When two heterozygotes are crossed (e.g., AaBb x AaBb) and the two loci (A/a and B/b) are linked, the segregation of the phenotypic traits in the F1 generation of a dihybrid cross is not in the usual 9:3:3:1 ratio.
- Linkage: This is the physical linkage of genes on the same chromosome. Linked genes are inherited together.
- If the genes are linked (no crossing over), only the parental phenotypes will be seen in the offspring.
- If the genes are partially linked (crossing over has taken place), both parental and recombinant phenotypes will be seen, but the parental phenotypes will occur more often than the recombinant phenotypes.
- For instance, Yellow body, white eyes, and wild-type parent cross in Drosophila. Hence, they are co-inherited in progenies. Parental types and recombinant types are 98.7% and 1.3%, respectively.
Q9. Briefly mention the contribution of T.H. Morgan to genetics.
Answer:
Contribution of T.H. Morgan to the discipline of genetics:
-
Chromosomal Theory of Inheritance: Morgan, along with his co-worker, presented better evidence of genes on chromosomes rather than the chromosomal theory of inheritance.
-
Sex-Linked Inheritance: Morgan showed sex-linked inheritance by studying Drosophila melanogaster and exhibiting that there are certain characteristics which are linked with sex chromosomes.
-
Linkage and Recombination: Morgan described the phenomenon of linkage (genes on the same chromosome are inherited together) and recombination (crossing over produces new combinations of alleles).
-
Mapping of Genes: Morgan's group established techniques to map the relative positions of genes on chromosomes in terms of recombination frequencies.
Q10. What is pedigree analysis? Suggest how such an analysis can be useful.
Answer:
Pedigree Analysis:
Definition: Pedigree analysis refers to the examination of the pattern of inheritance of a certain trait in a family line. It entails mapping a family pedigree and following the presence of the trait in generations.
Usefulness:
-
Determining Inheritance Pattern: Pedigree analysis determines if a trait is dominant, recessive, sex-linked, or autosomal.
-
Risk Prediction: It is possible to use it to estimate the likelihood of future offspring inheriting a given genetic condition.
-
Genetic Counselling: Genetic counsellors employ pedigree analysis to counsel families regarding their risk of having children with genetic disorders.
-
Identification of Carriers: Pedigrees can be used to identify carriers of recessive genetic disorders.
Q11. How is sex determined in human beings?
Answer:
Sex determination in human beings is on a chromosomal basis:
- Human beings possess 23 pairs of chromosomes: 22 pairs of autosomes and 1 pair of sex chromosomes.
- Females possess two X chromosomes (XX).
- Males possess one X and one Y chromosome (XY).
- In meiosis, females give rise to eggs that all carry an X chromosome.
- Males give rise to sperm that are either X-bearing or Y-bearing.
- If a sperm carrying X fertilises the egg, the child will be female (XX). If a Y-bearing sperm fertilises the egg, the child will be male (XY).
Thus, the offspring's sex is determined by the sperm.
Answer:
If the child has an O blood group, then it is evident that the parents are heterozygous. Thus, the genotype of the father will be IAi and that of the mother will be IBi . The child having blood group O will have genotype ii. The other children may have genotypes IAi (A blood group), IBi (B blood group) and IAIB (AB blood group).
Q13 . Explain the following terms with an example
Answer:
Codominance-
It refers to the phenomenon of two alleles lacking a dominant-recessive relationship and both expressing themselves in the heterozygous condition. In human beings, ABO blood grouping is controlled by gene I. The gene has three alleles I A, I B and i. One person may have any two of these three alleles. Among these alleles, I A, and I B are dominant over i. Alleles IA and IB. When I A and I B are present together, both express themselves because of co-dominance.
Answer:
Incomplete dominance-
Incomplete dominance is the phenomenon of neither of the two alleles being dominant, so that expression in the hybrid is a fine mixture or intermediate between the expressions of the two alleles. In snapdragon ( Mirabilis jalapa), there are two types of pure breeding plants, red-flowered and white flowered. On crossing the two, F1 plants possess pink flowers. On selfing them, F2 generation has 1red: 2 pink: 1white. The pink flower is due to incomplete dominance
Q14. What is a point mutation? Give one example.
Answer:
-
Point Mutation: A mutation which is a change at one point or location in the DNA sequence. It is a single-base pair or a few-base pair change.
-
Example: Sickle cell anaemia. The disease is caused by a single base substitution in the gene for the beta-globin chain of haemoglobin. The GAG to GUG substitution at the sixth codon causes glutamic acid to be replaced by valine, leading to abnormal haemoglobin that causes red blood cells to develop sickle shapes.
Q15. Who proposed the chromosomal theory of inheritance?
Answer:
Sutton and Baveri in 1902 proposed the chromosomal theory of inheritance.
Q16. Mention any two autosomal genetic disorders with their symptoms.
Answer:
Sickle Cell Anaemia:
-
Genetic Basis: Autosomal recessive disease due to a mutation of the gene for beta-globin on chromosome 11.
-
Symptoms: Chronic anaemia, pain crises, fatigue, susceptibility to infection, retarded growth, and organ damage.
Down Syndrome:
-
Genetic Basis: Autosomal disease due to trisomy 21 (an extra copy of chromosome 21).
-
Symptoms: Mental retardation, characteristic face (e.g., flat nose, slanted eyes), heart malformation, and other medical disorders.
Also, check the NCERT Books and the NCERT Syllabus here:
Approach to Solve Class 12 Biology Chapter 4 Question Answer
To solve the questions effectively, one needs to understand the concepts first. The chapter has certain key terms, such as Mendel's laws, monohybrid and dihybrid crosses, mutation and genetic disorders. Making notes of the chapter is important; students can do it by highlighting all the important points and terms. The NCERT Solutions for Class 12 Biology Chapter 4 Principles of Inheritance and Variation include answers in simple language and all necessary information. Students must practice these solutions to have an overall idea of the chapter and build confidence before the exams.
NCERT Solutions for Class 12- Subject-wise
- NCERT Solutions for Class 12 Maths
- NCERT Solutions for Class 12 Chemistry
- NCERT Solutions for Class 12 Physics
Recommended eBooks
Related eBooks & Sample Papers
Important Question from Class 12 Biology Chapter 4 Solutions
Given below is a solved practice question from this chapter. To gain clarity and improve their knowledge, students need to practice different types of questions to get familiar with the question pattern. For this purpose, students can depend on the Principles of Inheritance and Variation Class 12 NCERT Solutions.
Q1. Occasionally, a single gene may express more than one effect. The phenomenon is called:
Options:
1. Multiple allelism
2. Mosaicism
3. Pleiotropy
4. Polygeny
Answer:
The phenomenon known as pleiotropy refers to the expression of more than one effect by a single gene. This occurs when a gene is implicated in various biological pathways or processes, thereby influencing multiple, seemingly disparate traits or phenotypic attributes within an organism. A classic illustration of this is Marfan syndrome, a human genetic disorder resulting from a single gene mutation impacting connective tissue, which manifests in a spectrum of symptoms such as elongated limbs, cardiac issues, and ocular abnormalities.
Hence, the correct answer is option 3) Pleiotropy.
Also, Read the NCERT Syllabus for Class 12 Other Subjects
NCERT Syllabus for Class 12 Maths
NCERT syllabus for class 12 Chemistry
What Extra Should Students Study Beyond the NCERT for NEET?
Studying concepts beyond the NCERT will help in gaining conceptual clarity. It will also help in answering application-based questions, especially for competitive exams or school exams. Some extra concepts that can be studied are given below. Along with this, students need to practice diagrams, flow charts and definitions which are given in the Principles of Inheritance and Variation Class 12 NCERT Solutions.
NCERT Exemplar Class 12 Solutions
Below are the links for other NCERT exemplar class 12 solutions that students can use while preparing for the board exam or any competitive exam.
NCERT Solutions for Class 12 Biology: Chapter-wise
Below mentioned are the Chapter-wise solutions:
Frequently Asked Questions (FAQs)
Q: What are the important topics of NCERT Solutions for biology class 12 chapter 4?
A:
These are the important topics of the NCERT Solutions for Class 12 Biology Chapter 4 Principles of Inheritance and Variation are:
Mendel’s Laws of Inheritance
- Inheritance of One Gene
- Law of Dominance
- Law of Segregation
- Inheritance of Two Genes
- Sex Determination
- Mutation
- Genetic Disorders
- Mutation
- Genetic disorders
Q: what are the mendel's laws of inheritance given in biology class 12 chapter 4 pdf?
A:
As Mendel proposed the principles of inheritance, which are today referred to as ‘Mendel’s Laws of Inheritance’. There are different types of law that you will study in the principle of inheritance and variation ncert pdf. For example:
- Law of Dominance
- Law of Segregation
- Law of Independent Assortment, etc.
All these three laws, along with the punett square, are well explained in the NCERT Solutions for Class 12 Biology Chapter 4 Principles of Inheritance and Variation.
Q: How to download NCERT Solutions for Class 12 Biology Chapter 4?
A:
Students can download the Principles of Inheritance and Variation Class 12 NCERT Solutions from the Careers360 page, which is
https://school.careers360.com/ncert/ncert-solutions-class-12-biology-chapter-4
Q: What is the difference between dominant and recessive traits?
A:
Dominant Traits: Expressed even if only one dominant allele is present (e.g., BB or Bb).
Recessive Traits: Only expressed when both alleles are recessive (e.g., bb). Dominant alleles mask recessive traits.
These basic concepts are clearly explained in the Principles of Inheritance and Variation NCERT PDF, which helps students understand genetic traits with simple examples.
Q: What are multiple alleles and co-dominance?
A:
The difference between multiple alleles and co-dominance is given below. For more detailed information students can refer to Class 12 Biology Chapter 4 question answer.
Multiple Alleles: More than two alleles exist for a gene (e.g., ABO blood group system).
Co-dominance: Both alleles in a heterozygote are equally expressed (e.g., AB blood type).
Articles
Related Stories
|
Upcoming School Exams
Certifications By Top Providers
Explore Top Universities Across Globe
University of Essex, Colchester
Wivenhoe Park Colchester CO4 3SQUniversity College London, London
Gower Street, London, WC1E 6BTThe University of Edinburgh, Edinburgh
Old College, South Bridge, Edinburgh, Post Code EH8 9YLUniversity of Delaware, Newark
Newark, DE 19716University of Nottingham, Nottingham
University Park, Nottingham NG7 2RDBristol Baptist College, Bristol
The Promenade, Clifton Down, Bristol BS8 3NJQuestions related to CBSE Class 12th
On Question asked by student community
Have a question related to CBSE Class 12th ?
Hello Aspirant,
Yes, in the case that you appeared for the 2025 improvement exam and your roll number is different from what was on the previous year’s marksheet, the board will usually release a new migration certificate. This is because the migration certificate will reflect the most recent exam details, roll number and passing year. You can apply to get it from your board using the process prescribed by them either online or through your school/college.
Hello,
Yes, you can. If you missed the first compartment exam, you can appear in the second compartment exam as per CBSE rules.
Hope it helps !
Hello Prisha
As you have compartment in Mathematics and you wish to change your stream to Humanities you have 2 options from here on:
1. You could try to study and clear your compartment of Mathematics.
2. You can change your stream to Humanities but you will need to repeat from Class 11th so you will need 2 years from now to clear Class 12th.
My personal suggestion will be to choose Option 1. Trust me I have dealt with this feeling myself and wanted to choose Option 2 but I worked hard and cleared my exams. I was scared not only in Mathematics but Physics, Chemistry and even Computer Science.
At last, it's on you what you want to choose.
Thank You!
HELLO,
The GUJCET merit list is calculated by considering 60% of the marks obtained in Class 12 and 40% of the GUJCET score. CBSE students are also eligible to compete with GSEB students, as the merit list is prepared by combining the Class 12 scores with the GUJCET performance.
Merit Calculation:
- The merit list is calculated by combining the scores from both class and the GUJCET exam
- This means that both your performance in the class 12 board exams and the GUJCET exam are considered when determining your rank
CBSE Students and GUJCET:
- CBSE students can appear for the GUJCET exam, even though they are not from the Gujrat Board
- For CBSE students, the 60% weightage for class 12 marks will be based on their performance in Physics, Chemistry, and Mathematics in their class 12 board exams
- The remaining 40% weightage will be given to their GUJCET score.
Hope this Helps!
Hello Aspirant,
Yes, your CBSE migration certificate from March 2024 is totally good for reporting in 2025. These certificates do not randomly expire or anything. As long as you’ve got the real one and it is not scribbled then it is fine. No one’s gonna hassle you about the date, just make sure it’s in decent shape and you’re all set.
Popular CBSE Class 12th Questions
A block of mass 0.50 kg is moving with a speed of 2.00 ms-1 on a smooth surface. It strikes another mass of 1.00 kg and then they move together as a single body. The energy loss during the collision is
| Option 1)
|
Option 2)
|
| Option 3)
|
Option 4)
|
An athlete in the olympic games covers a distance of 100 m in 10 s. His kinetic energy can be estimated to be in the range
| Option 1)
|
Option 2)
|
| Option 3)
|
Option 4)
|
A particle is projected at 600 to the horizontal with a kinetic energy . The kinetic energy at the highest point
| Option 1)
|
Option 2)
|
| Option 3)
|
Option 4)
|
In the reaction,
| Option 1)
|
Option 2)
|
| Option 3)
|
Option 4)
|
How many moles of magnesium phosphate, will contain 0.25 mole of oxygen atoms?
| Option 1)
0.02 |
Option 2)
3.125 × 10-2 |
| Option 3)
1.25 × 10-2 |
Option 4)
2.5 × 10-2 |
Colleges After 12th
Study Resources, Applications and Opportunities
Aakash Repeater Courses
ApplyTake Aakash iACST and get instant scholarship on coaching programs.
NEET Most scoring concepts
Get nowThis ebook serves as a valuable study guide for NEET 2025 exam.
NEET Previous 10 Year Questions
Get nowThis e-book offers NEET PYQ and serves as an indispensable NEET study material.
JEE Main Important Physics formulas
Get nowAs per latest syllabus. Physics formulas, equations, & laws of class 11 & 12th chapters
JEE Main Important Chemistry formulas
Get nowAs per latest syllabus. Chemistry formulas, equations, & laws of class 11 & 12th chapters
JEE Main high scoring chapters and topics
Get nowAs per latest 2024 syllabus. Study 40% syllabus and score upto 100% marks in JEE
CBSE Class 12th Notifications
Never miss an CBSE Class 12th update
Get timely CBSE Class 12th updates directly to your inbox. Stay informed!