CBSE Class 11 Biology Cell Cycle and Cell Division Important Questions - FREE PDF Download
1 Marks Questions:
1. Name the stage of cell division in which paired homologous chromosomes get shortened and thickened?
Ans: Pachytene is the stage of cell division in which paired homologous chromosomes get shortened and thickened.
2. Which structure of animal cell forms the asters of the spindle?
Ans: The centrosome is the structure of an animal cell that forms the asters of the spindle.
3. Name the cells in which meiosis occurs?
Ans: Meiosis occurs in the reproductive cells or germ cells.
4. At which stage of meiosis crossing over of genetic material takes place?
Ans: Pachytene is the stage of meiosis in which the crossing over of genetic material takes place.
5. What is the Go phase?
Ans: A stage when the cell cycle is arrested during interphase is called the Go phase.
6. Name the cell division concerned with cancer?
Ans: Mitosis is the type of cell division that is concerned with cancer.
7. What are kinetochores?
Ans: Kinetochores are small disc-shaped structures at the surface of the centromeres.
8. What is interkinesis?
Ans: Interkinesis is the stage between two meiotic divisions.
9. Why is mitosis called equational division?
Ans: The chromosome number in the daughter cells is equal to the number of chromosomes in the parent cell hence mitosis is called equational division.
10. Name the stage of meiosis during which synaptonemal complex is formed.
Ans: Zygotene is the stage of meiosis during which a synaptonemal complex is formed.
11. What is the Go phase of the cell cycle?
Ans: Go is that phase of a cell cycle where the cells are metabolically active but no longer proliferate.
12. Where does mitosis take place in plants and animals?
Ans: In plants mitosis takes place in the meristematic tissues whereas, in animals, it occurs in the somatic cells.
2 Marks Questions:
1. What is the importance of chromosomes replication during interphase?
Ans: Interphase is a stage between successive cell divisions. It is considered as the resting stage of a nucleus because it does not show any changes in the morphology however, physiologically it is an active stage in the life of a cell as the cell prepares itself for division and other biochemical changes as well.
2. Distinguish between the metaphase of mitosis and metaphase I of meiosis?
Ans: The metaphase of mitosis and metaphase I of meiosis differ from each other as:
Metaphase of mitosis | Metaphase of meiosis: I |
Each chromosome consists of two chromatids held together by the centromere. | Homologous chromosomes form bivalent and each bivalent consists of four chromatids along with two centromeres. |
Chromosomes line up in one plane to make up an equatorial plate. | Bivalents become arranged in the plane of the equator forming an equatorial plate. |
3. How does duration affect the cell cycle in an organism?
Ans: Duration depends on the type of cell and other external factors such as temperature, food, and oxygen. The time period for G, S, G, and M-phase in different species under specific environmental conditions is like 20 min for bacterial cells, 10 hours for intestinal epithelial cells, 20 hours for onion root tip cells, etc. This shows that the time required for each step has been pre-set within cells of each organism.
4. Why is meiosis called reductional division and mitosis called equational division?
Ans: In meiosis, the number of chromosomes gets reduced to half hence, it is known as reductional division. Gametes are formed in sexually reproducing organisms in the germ cell. In mitosis, the number of chromosomes remains constant after division therefore, it is called equational division.
5. Write three processes that take place in interphase?
Ans: The three processes in interphase are:
i. Replication of DNA with the synthesis of histones and nuclear proteins.
ii. Division of the centriole to new centriole which lies at right to each other.
iii. Synthesis of energy-rich compounds to provide energy for mitosis.
6. Enumerate the significance of mitosis?
Ans: The various significances of mitosis are:
i. The number of chromosomes in the mitosis cell division remains constant in daughter cells.
ii. Asexual reproduction occurs with the help of mitosis.
iii. The size of a cell is controlled by the process of mitosis.
iv. The growth and development of the zygote are maintained by the process of mitosis.
7. Differentiate between chromatin and chromate.
Ans: Chromatin and chromate differ from each other as:
Chromatin | Chromatid |
It is the diffused, deep staining hereditary material. | It is longitudinally split half of a chromosome, light staining hereditary material. |
It is metabolically inert | It is metabolically active |
8. Give the terms for the following:
a. The pet between 2 successive mitotic divisions.
b. Colt division in which chromosome number is halved.
c. Phase in the cell cycle where DNA is synthesized.
d. Division of nuclear material.
Ans:
a. Interphase
b. Meiosis
c. S phase
d. Karyokinesis
3 Marks Questions:
1. What is the significance of meiosis?
Ans: The significance of meiosis is:
a. Meiosis reduces the number of chromosomes to half in the daughter cells.
b. Meiosis is a process in sexually reproducing animals because it restores the fixed number of chromosomes.
c. Meiosis results in the formation of gametes. Each of these gametes possesses half the number of chromosomes present in the somatic cells.
d. Gametes avoid multiplication of chromosomes thus maintaining the stability and a constant number of chromosomes of the species.
e. During crossing over, the exchange of nuclear material, genetic variations within the species occurs resulting in a new combination of genetic material.
2. Differentiate between animal cell mitosis & plant cell mitosis?
Ans: Animal cell mitosis and plant cell mitosis differ from each other as:
Animal Cell Mitosis | Plant Cell Mitosis |
It occurs in the bone marrow | It occurs in the meristems |
The animal cell becomes spherical before the division of the cell | The shape of the cell does not change before division |
Multiple hormones are involved in the cell division | It is induced by plant hormone cytokine only |
Presence of centrosome | Absence of centrosome |
The mitotic apparatus have asters | The mitotic apparatus lacks asters |
Midbody is formed | Midbody is not formed |
It occurs through cleavage | It occurs by cell-plate formation |
Microfilaments are involved in it | No microfilaments are formed |
In this, cleavage proceeds centripetally | In this, the cell grows centrifugally |
3. Write six differences between mitosis & meiosis?
Ans: Mitosis and meiosis differ from each other as:
Mitosis | Meiosis |
In this process, the doubling of the chromosome is followed by separation of the daughter chromosomes hence, the cell divides once only | In this process, the doubling of chromosomes occurs once but it is followed by two nuclear divisions hence, the cell divides twice |
It occurs in all the somatic cells | It occurs in only reproductive or germ cells |
It is completed in one sequence of stages | The whole process completes in two successive divisions |
Synopsis is absent | Synopsis is present |
No crossing over or formation of chiasmata | Both crossing over and formation of chiasmata occurs |
A cell produces two diploid cells | A cell produces four haploid cells |
4. What are homologous chromosomes? What happens to homologous chromosomes during meiosis?
Ans: Homologous chromosomes are defined as pairs of similar chromosomes having corresponding genes governing the same set of traits.
During the heterotypic division of meiosis in leptotene, the chromosomes are thread-shaped and are coiled. During zygotene, homologous chromosomes start pairing. In pachytene, chromosomes show both- thickening and shortening. Diplotene is marked by the cessation of attraction force between the two homologous chromosomes. Uncoiling of the homologous chromosomes separate them from each other but also remains attached at chiasmata. During diakinesis, the separation of the homologous chromosome is complete. Exchange of parts between chromatids of homologous chromosomes may take place. During Anaphase I, centromeres of homologous compounds of bivalents repel each other post the separation of the centromere. The homologous chromosomes start to move apart, in telophase-I, chromosomes reach poles and become shortened.
5. What will be the DNA content of a cell at G1, after S and G2., if the content after the M phase is 2C.
Ans:
Before mitotic division, the cell is in the interphase. There are three phases in interphases G1, S, G2. The daughter cell grows in size and produces the enzyme required for replication in the G1 phase.
In the S phase, DNA replicates and the content of the chromosome gets double. In the G2 phase, cells grow in size and prepare to move in mitosis.
Hence, when DNA content after the M-phase of a cell is 2c then in the G1 phase it remains in 2c as no replication occurs in this phase.
In the S phase, DNA content becomes 4c as DNA replication takes place in this stage, and in the G2 phase, the DNA content will remain 4c.
Then, when this cell finishes mitosis, the DNA content gets reduced to half i.e, 2c.
G1-2C1S-4C, G2-4C
5 Marks Questions:
1. Explain the various phases of meiosis II division?
Ans: Stages of meiosis II are:
i. Prophase II: Meiosis II is initiated immediately after cytokinesis usually before chromosomes have fully elongated. The nuclear membrane disappears by the end of prophase-II. The chromosomes again become compact.
ii. Metaphase-II: At this stage, the chromosomes align at the equator & the microtubules from opposite poles of the spindle get attached to the kinetochores of sister chromatids.
iii. Anaphase-II: It begins with the simultaneous splitting of the centromere of each chromosome allowing them to move towards opposite poles of the cell.
iv. Telophase-II: Meiosis ends with telophase-II, in which two groups of chromosomes once again get enclosed by the nuclear envelope, cytokinesis follows resulting in the formation of the tetrad of cell i.e. four haploid daughter cells.
2. What is mitosis? Give a brief account of mitosis in an animal cell?
Ans: Mitosis is an equational cell division in which the number of chromosomes in parent and, progeny cell remains the same.
Stages of mitosis:
i. Prophase:
a. Chromosome material condenses to form compact mitotic chromosomes. Chromosomes are seen to be composed of two chromatids attached together at the centromere.
b. Initiation of assembly of the mitotic spindle, microtubules the protein components of the cell cytoplasm help in the process.
ii. Metaphase:
a. Spindle fibers attach to kinetochores of chromosomes
b. Chromosomes are moved to the spindle equator and get aligned along with the metaphase plate through spindle fibers to both poles.
iii. Anaphase:
a. Centromere splits and chromatids separate
b. Chromatids move to the opposite poles.
iv. Telophase:
a. Chromosomes cluster at opposite spindle poles and lose their identity.
b. The nuclear envelope assembles around the clusters of chromosomes.
c. Nucleolus, Golgi complex, and the ER reform.
The different stages of mitosis.
Important Study Materials for Class 11 Biology Chapter 10
Access Chapterwise Links to CBSE Class 11 Biology - Important Questions - FREE PDF
Additional Study Materials for Class 11 Biology
FAQs on Important Questions for CBSE Class 11 Biology Chapter 10 - Cell Cycle and Cell Division
1. What are the most important 5-mark questions from the topic Cell Cycle and Division for Class 11 CBSE 2025–26 exams?
- Phases of meiosis II with detailed description
- Explain mitosis and its stages in an animal cell
- Compare and contrast mitosis and meiosis, listing at least six differences
- Describe the regulation and significance of cell cycle checkpoints
- Discuss the significance of meiosis in maintaining chromosome number and genetic variation, with examples
2. Which cell cycle and division questions are frequently asked for 3 marks in Class 11 Biology board exams?
- Significance of meiosis in living organisms
- Distinguish between plant cell mitosis and animal cell mitosis
- Write the major differences between metaphase of mitosis and metaphase I of meiosis
- Explain what happens to homologous chromosomes during meiosis
- Calculate DNA content at G1, S, and G2 phases if the M phase content is given
3. What is a commonly misunderstood concept about the Go phase in the cell cycle for Class 11 students?
The Go phase is often confused as a passive state where nothing happens. In reality, cells in Go are metabolically active but do not proliferate. Cells can remain in Go temporarily or permanently, depending on their type and function.
4. How can I identify high-weightage areas within the Cell Cycle and Division chapter for CBSE Class 11 exams?
- Focus on phases and events of mitosis and meiosis (mechanisms, diagrams, and differences)
- Cell cycle regulation and checkpoints (conceptual short answer and HOTS)
- Process and significance of crossing over during meiosis
- Comparison tables: mitosis vs. meiosis, animal vs. plant cell mitosis
- Short factuals: Go phase, interphase events, chromosome terminology
5. Why is meiosis considered reductional division and what exam mistakes do students commonly make here?
Meiosis is called reductional division because it halves the chromosome number, producing haploid cells from diploid parents. Students often mistake this for mitosis, or incorrectly state that reduction occurs in both divisions of meiosis rather than specifically in meiosis I.
6. What type of conceptual application questions are likely in Cell Cycle and Division important questions for Class 11?
CBSE papers now include HOTS such as: describe what would happen if checkpoint mechanisms fail; predict the effect of a non-functional spindle apparatus; analyze DNA content changes during various cell cycle phases; or infer outcomes if crossing over is inhibited during meiosis.
7. How can questions on chromatin and chromatid be framed for 1 mark in board exams?
A typical 1-mark question may be: Define chromatin and chromatid, or distinguish between them in a single sentence as per CBSE guidelines for direct short answer format.
8. What are exam-focused differences between mitosis and meiosis every Class 11 student must memorise?
- Mitosis: Occurs in somatic cells, 1 cell cycle, produces 2 identical diploid cells, no crossing over or synopsis
- Meiosis: Occurs in germ cells, 2 consecutive divisions, results in 4 genetically distinct haploid cells, crossing over and synopsis present
- Additional: Chiasmata form only in meiosis, chromosome number unchanged in mitosis, halved in meiosis—all as per CBSE marking scheme (2025–26)
9. What are some hot concept-based traps in cell cycle and division important questions for CBSE Class 11?
- Confusing metaphase arrangements in mitosis vs. meiosis
- Misstating Go phase as cell death
- Incorrectly assigning functions to centrosomes vs. centromeres
- Mixing up terms like chromatin, chromatid, chromate
- Believing DNA content is always halved after cell division—in reality, it depends on the division type
10. What are the expected 1-mark factuals from Cell Cycle and Division in Class 11 Biology for 2025–26 exams?
- Name the stage of meiosis where crossing over happens (Answer: Pachytene)
- Which animal cell structure forms the spindle asters? (Answer: Centrosome)
- Cells where meiosis occurs (Answer: Germ or reproductive cells)
- State why mitosis is called equational division (Answer: Daughter and parent cells have equal chromosome number)
11. How might CBSE test knowledge of checkpoint failure in the cell cycle?
Exam questions may ask students to explain potential outcomes if G1, G2, or M phase checkpoints fail—such as rapid, uncontrolled cell division leading to mutations or cancer, or cell cycle arrest due to DNA damage.
12. What is the significance of the S phase in interphase, as asked in previous board exams?
The S phase is marked by DNA synthesis and duplication, ensuring genetic material is accurately replicated for distribution during mitosis or meiosis. Errors in this phase can result in genetic disorders or cell malfunction.
13. Which 2-mark Cell Cycle and Division questions target marking weightage best?
- Explain the importance of chromosome replication during interphase (CBSE 2025–26 priority)
- Give three main events of interphase
- List three significances of mitosis in multicellular organisms
14. What should students focus on when preparing important questions from Cell Cycle and Division for NEET and board?
Prioritize differences between mitosis and meiosis, stages and significance of each phase, checkpoint control mechanisms, and conceptual HOTS involving prediction and analysis based on cell cycle disruptions—aligning with high-weightage exam questions.
15. How can misunderstanding the processes of mitosis or meiosis affect answers in CBSE Biology exams?
Poor differentiation between the two processes leads to wrong answers, especially in comparison or significance questions. Students must emphasize the number of divisions, chromosome behavior, and genetic outcomes when answering Cell Cycle and Division important questions for Class 11 CBSE (2025–26).
