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 solutionshelp students clarify their concepts and improve their performance in board exams as well as entrance exams, such as NEET.
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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
NCERT Solutions for Class 12 Biology Chapter 4 Principles of Inheritance and Variation
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.
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.
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.
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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.
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).
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):
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
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.
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.
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.
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).
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.
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
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.
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.
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
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.
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).
If you want to improve the Class 12 PCM results, you can appear in the improvement exam. This exam will help you to retake one or more subjects to achieve a better score. You should check the official website for details and the deadline of this exam.
SASTRA University commonly provides concessions and scholarships based on merit in class 12 board exams and JEE Main purposes with regard to board merit you need above 95% in PCM (or on aggregate) to get bigger concessions, usually if you scored 90% and above you may get partial concessions. I suppose the exact cut offs may change yearly on application rates too.
CBSE generally forwards the marksheet for the supplementary exam to the correspondence address as identified in the supplementary exam application form. It is not sent to the address indicated in the main exam form. Addresses that differ will use the supplementary exam address.
To find Class 12 Arts board papers, go to the official website of your education board, then click on the Sample Papers, Previous Years Question Papers(PYQ) or Model Papers section, and select the Arts stream. You will find papers for the various academic year. You can then select the year of which you want to solve and do your practice. There are many other educational websites that post pyqs on their website you can also visit that.
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