CBSE Class 12 Biology Sexual Principles of Inheritance And Variation Worksheet

Official Class 12 Biology Worksheets: Chapter 4 Principles of Inheritance and Variation

Explore reliable practice materials for Chapter 4 Principles of Inheritance and Variation tailored for Class 12 learners. Utilizing these Biology worksheets ensures thorough preparation and strengthens problem-solving speed for upcoming school assessments.

Chapter-wise Practice Material: Chapter 4 Principles of Inheritance and Variation

View or download the dedicated Chapter 4 Principles of Inheritance and Variation practice resource below. Engaging with these objective and subjective questions daily ensures continuous academic progress and mastery of the 2026-27 curriculum.

MULTIPLE CHOICE QUESTIONS

Question. Pure line breed refers to 
(a) homozygosity
(b) heterozygosity
(c) linkage
(d) both b & c
Answer. A

Question.Given below is a pedigree chart of a family with five children. It shows the inheritance of attached earlobes as opposed to the free ones. The squares represent the male individuals and circles the female individuals. Which one of the following conclusions drawn is correct?
CBSE Class 12 Biology Principles of Inheritance And Variation

(a) The parents are homozygous recessive.
(b) The trait is Y-linked.
(c) The parents are homozygous dominant.
(d) The parents are heterozygous.
Answer. D

Question. If a homozygous red flowered plant is crossed with a homozygous white flowered plant, the offsprings would be [2002]
(a) all red flowered
(b) half red flowered
(c) half white flowered
(d) all white flowered
Answer. A

Question. Which disease has XXY chromosome constitution?
(a) Down’s syndrome 
(b) Turner’s syndrome
(c) Klinefelter’s syndrome
(d) Okazaki syndrome
Answer. C

Question. Barr-body in mammals represents 
(a) One of the two X chromosomes in somatic cells of females.
(b) All heterochromatin of male & female cells.
(c) Y chromosomes of male.
(d) All heterochromatin of female cells
Answer. A

Question. Genes of which one of the following is present exclusively on the X-chromosome in humans?
(a) Baldness
(b) Red-green colour blindness
(c) Facial hair/moustaches in males
(d) Night blindness
Answer. B

Question. XO chromosomal abnormality in humans causes
(a) Turner’s syndrome
(b) Down’s syndrome
(c) Patau’s syndrome
(d) Klinefelter’s syndrome
Answer. A

Question. Mirabilis jalapa shows 
(a) codominance
(b) incomplete dominance
(c) dominance
(d) complementary genes
Answer. B

Question. The formation of multivalents at meiosis in diploid organism is due to 
(a) monosomy
(b) deletion
(c) inversion
(d) reciprocal translocation
Answer. D

Question. In India, we find mangoes with different flavours, colours, fibre content, sugar content and even shelf-life. The large variation is on account of
(a) species diversity
(b) induced mutations
(c) genetic diversity
(d) hybridization
Answer. C

Question. Which one of the following pairs of features is a good example of polygenic inheritance?
(a) Human height and skin colour.
(b) ABO blood group in humans and flower colour of Mirabilis jalapa.
(c) Hair pigment of mouse and tonque rolling in humans.
(d) Human eye colour and sickle cell anaemia.
Answer. A

Question. Gene which suppresses other gene’s activity but does not lie on the same locus is called as
(a) epistatic
(b) supplementary
(c) hypostatic
(d) codominant
Answer. A

Question. Polygenic genes show 
(a) similar genotype
(b) different phenotype
(c) different karyotype
(d) different genotype
Answer. B

Question. In Huntington’s disease, the unaffected persons are homozygous for normal allele h. The following is erroneous because
CBSE Class 12 Biology Principles of Inheritance And Variation

B-142 Topicwise AIIMS Solved Papers – BIOLOGY
(a) it shows both male and female affected by Huntingtons disease
(b) either person 6 or 7 should have the disease, if individual 11 shows the disease.
(c) at least one of the 2 children (8, 9) should have the disease
(d) all of these
Answer. B

Question. Discontinuous variations are 
(a) essential features
(b) acquired characters
(c) non-essential changes
(d) mutations
Answer. D

Question. Bird females have chromosome arrangement as
(a) XY
(b) XO
(c) WZ
(d) WW
Answer. C

Question. Gene pool is referred to 
(a) the genetic drift caused in a population
(b) aggregate of all genes and their alleles in a population.
(c) deletion of non essential genes.
(d) induce cell division
Answer. B

Question. Given below is a highly simplified representation of the human sex chromosomes from a karyotype.
CBSE Class 12 Biology Principles of Inheritance And Variation

The genes a and b could be of
(a) colour blindness and body height
(b) attached ear lobe and Rhesus blood group
(c) haemophilia and red-green colour blindness
(d) phenylketonuria and haemophilia
Answer. C

ASSERTION REASON QUESTIONS

Directions : These questions consist of two statements, each printed as Assertion and Reason. While answering these questions, you are required to choose any one of the following five responses.
(a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
(b) If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
(c) If the Assertion is correct but Reason is incorrect.
(d) If both the Assertion and Reason are incorrect.
(e) If the Assertion is incorrect but the Reason is correct.

Question. Assertion : The genetic complement of an organism is called genotype.
Reason : Genotype is the type of hereditary properties of an organism. 
Answer. A

Question. Assertion : Phenylketonuria is a recessive hereditary disease caused by body’s failure to oxidize an amino acid phenylalanine to tyrosine, because of a defective enzyme.
Reason : It results in the presence of phenylalanine acid in urine. 
Answer. B

Question. Assertion : In humans, the gamete contributed by the male determines whether the child produced will be male or female.
Reason : Sex in humans is a polygenic trait depending upon a cumulative effect of some genes on X-chromosome and some on Y-chromosome. 
Answer. C

Question. Assertion : Haemophilia is a recessive sex linked disease.
Reason : Haemophilia occurs due to mutation of a structural gene on chromosome 15
Answer. C

PRINCIPLES OF INHERITANCE AND VARIATION
 
1. Name one autosomal dominant and one autosomal recessive Mendelian disorder in humans.
 
2. Write the genotype of i) an individual who is carrier of sickle cell anaemia gene but apparently unaffected, and ii) an individual affected with the disease.
 
3. A human being suffering from Down’s syndrome shows trisomy of 21st chromosome. Mention the cause of this chromosomal abnormality.
 
4. Write the percentage of F2 homozygous and heterozygous populations in a typical monohybrid cross.
 
5. A man with blood group A married a woman with B group. They have a son with AB blood group and a daughter with blood group O. Workout the cross and show the possibility of such inheritance.
 
6. The male fruit fly and female fowl are heterogametic while the female fruit fly and male fowl are homogametic. Why are they called so?
 
7. A plant of Antirrhinum majus with red flowers was crossed with another plant of the same species with white flowers. The plants of the F1 generation bore pink flowers. Explain the pattern of inheritance with the help of a cross.
 
8. A woman with blood group ‘O’ married a man with AB group. Show the possible blood groups of the progeny. List the alleles involved in this inheritance.
 
9. How does a test cross help in identifying the genotype of the organism? Explain.
 
10. When a tall pea plant was selfed, it produced one fourth of its progeny as dwarf. Explain with the help of a cross.
 
11. i) Why are grasshopper and Drosophila said to show male heterogamety? Explain.
ii) Explain female heterogamety with the help of an example.
 
12. Explain the pattern of inheritance of haemophilia in humans. Why is the possibility of a human female becoming haemophilic extremely rare? Explain.
 
13. A non-haemophilic couple was informed by their doctor that there is possibility of a haemophilic child be born to them. Explain the basis on which the doctor conveyed this information. Give the genotypes and the phenotypes of all the possible children who could be born to them
 
14. Study the pedigree chart and answer the questions that follow:
CBSE Class 12 Biology Sexual Principles of Inheritance And Variation Worksheet 1
 
a) Is the trait recessive or dominant?
b) Is the train sex- linked or autosomal?
c) Give the genotypes of the parents shown in generation I and their third child shown in generation II and the first grand child shown in generation III.
 
15. Haemophilia is a sex linked recessive disorder of humans. The pedigree chart given below shows the inheritance of haemophilia in one family. Study the pattern of inheritance and answer the questions given.
CBSE Class 12 Biology Sexual Principles of Inheritance And Variation Worksheet 2
a) Give all the possible genotypes of the members 4,5 and 6 in the pedigree chart.
b) A blood test shows that the individual 14 is a carrier of haemophilia. The member numbered 15 has recently married the member numbered 14. What is the probability that their first child will be haemophilic male?
 
16. Inhertiance pattern of ABO blood groups in humans shows dominance, codominance and multiple allelism. Explain each concept with the help of blood group genotypes.
 
17. Who proposed chromosomal theory of inheritance? Point out any two similarities in the behaviour of chromosomes and genes.
 
18. Explain the sex determination mechanism in humans. How is it different in birds.
 
19. Explain the mechanism of sex determination in insects like Drosophila and grasshopper.

 

Please click on below link to download CBSE Class 12 Biology Sexual Principles of Inheritance And Variation Worksheet

Free study material for Biology

Chapter 4 Principles of Inheritance and Variation Practice Sheet and Solutions for Class 12 Biology

CBSE Practice Material: Class 12 Biology Chapter 4 Principles of Inheritance and Variation

Access structured practice worksheets for Chapter 4 Principles of Inheritance and Variation designed in alignment with the latest CBSE curriculum for Class 12 Biology. These printable problem sets help students build accuracy and prepare effectively for school tests.

NCERT-Aligned Questions and Solutions

Cross-reference your completed exercises with comprehensive NCERT solutions for Class 12 Biology to ensure absolute clarity across all sub-topics in this chapter.

Next Steps in Your Exam Preparation

Follow up your worksheet practice by attempting the interactive online Biology MCQ test for this chapter to evaluate your execution speed. All platform resources are free to access.

FAQs

Where can I download the latest PDF for CBSE Class 12 Biology Sexual Principles of Inheritance And Variation Worksheet?

You can download the teacher-verified PDF for CBSE Class 12 Biology Sexual Principles of Inheritance And Variation Worksheet from StudiesToday.com. These practice sheets for Class 12 Biology are designed as per the latest CBSE academic session.

Are these Biology Class 12 worksheets based on the 2026-27 competency-based pattern?

Yes, our CBSE Class 12 Biology Sexual Principles of Inheritance And Variation Worksheet includes a variety of questions like Case-based studies, Assertion-Reasoning, and MCQs as per the 50% competency-based weightage in the latest curriculum for Class 12.

Do you provide solved answers for CBSE Class 12 Biology Sexual Principles of Inheritance And Variation Worksheet?

Yes, we have provided detailed solutions for CBSE Class 12 Biology Sexual Principles of Inheritance And Variation Worksheet to help Class 12 and follow the official CBSE marking scheme.

How does solving CBSE Class 12 Biology Sexual Principles of Inheritance And Variation Worksheet help in exam preparation?

Daily practice with these Biology worksheets helps in identifying understanding gaps. It also improves question solving speed and ensures that Class 12 students get more marks in CBSE exams.

Is there any charge for the Class 12 Biology practice test papers?

All our Class 12 Biology practice test papers and worksheets are available for free download in mobile-friendly PDF format. You can access CBSE Class 12 Biology Sexual Principles of Inheritance And Variation Worksheet without any registration.