Chapter 10: Cell Cycle and Cell Division – Short Answer Type Questions

CBSE Class 11 Biology Short Answer Questions – Cell Cycle and Cell Division (Chapter 10 | NCERT)

Course & Examination Details (Systematic Format)

Course: CBSE Class 11 Biology
Unit: III – Cell Structure and Function
Chapter: 10 – Cell Cycle and Cell Division
Based on: NCERT Textbook
Examination: CBSE Board Examination (Class XI)
Assessment Focus: Flowcharts, stage-wise comparison, conceptual clarity

Section A: Cell Cycle and Its Phases (Q1–Q15)

Q1. Define the cell cycle and explain its importance.
Answer:
The cell cycle is the sequence of events by which a cell grows, duplicates its genetic material, and divides into daughter cells. It is essential for growth, tissue repair, replacement of worn-out cells, and maintenance of genetic continuity in organisms.

Q2. Name and briefly explain the two main phases of the cell cycle.
Answer:
The two main phases are interphase and M phase. Interphase involves cell growth and DNA replication, while M phase includes mitosis and cytokinesis, leading to the formation of daughter cells.

Q3. Why is interphase considered the most active phase of the cell cycle?
Answer:
Interphase is metabolically active because the cell synthesizes proteins, RNA, enzymes, duplicates organelles, and replicates DNA, preparing itself for successful cell division.

Q4. Describe the events of the G₁ phase.
Answer:
During G₁ phase, the cell grows in size, synthesizes proteins and RNA, and duplicates organelles. It also checks internal and external conditions before entering DNA synthesis.

Q5. What is the significance of the S phase?
Answer:
In the S phase, DNA replication occurs, resulting in duplication of chromosomes into sister chromatids. This ensures accurate transmission of genetic information to daughter cells.

Q6. What changes occur during the G₂ phase?
Answer:
G₂ phase involves further growth of the cell, synthesis of spindle fibers and tubulin proteins, and repair of DNA if required, preparing the cell for mitosis.

Q7. What is the G₀ phase?
Answer:
G₀ phase is a quiescent stage where cells exit the cell cycle and stop dividing temporarily or permanently, while remaining metabolically active.

Q8. Differentiate between interphase and M phase.
Answer:
Interphase is the preparatory stage involving growth and DNA replication, whereas M phase is the division stage involving mitosis and cytokinesis, resulting in daughter cells.

Q9. Why is DNA replication necessary before cell division?
Answer:
DNA replication ensures that each daughter cell receives an identical and complete set of genetic material, maintaining genetic stability.

Q10. What is cytokinesis? Mention its significance.
Answer:
Cytokinesis is the division of cytoplasm following nuclear division. It ensures physical separation of daughter cells, completing the process of cell division.

Q11. How does cytokinesis differ in plant and animal cells?
Answer:
In animal cells, cytokinesis occurs by cleavage furrow formation, while in plant cells, a cell plate forms due to the presence of a rigid cell wall.

Q12. Why is regulation of the cell cycle important?
Answer:
Proper regulation ensures controlled cell division. Uncontrolled division can lead to abnormal growth and diseases like cancer.

Q13. What ensures genetic stability during the cell cycle?
Answer:
Accurate DNA replication during S phase and equal distribution of chromosomes during mitosis ensure genetic stability.

Q14. Name the checkpoint phases of the cell cycle.
Answer:
Major checkpoints occur during G₁, G₂, and metaphase, ensuring proper conditions and accurate chromosome alignment.

Q15. State one function of the cell cycle in multicellular organisms.
Answer:
The cell cycle enables growth and development by increasing the number of cells.

Section B: Mitosis (Q16–Q30)

Q16. Define mitosis.
Answer:
Mitosis is an equational division in which a parent cell divides to form two genetically identical daughter cells with the same chromosome number.

Q17. Name the stages of mitosis in correct order.
Answer:
The stages of mitosis are prophase, metaphase, anaphase, and telophase.

Q18. Describe the major events of prophase.
Answer:
During prophase, chromatin condenses into chromosomes, nuclear membrane and nucleolus disappear, and spindle fibers begin to form.

Q19. Why is metaphase important for chromosome study?
Answer:
Chromosomes are maximally condensed and aligned at the equatorial plane, making metaphase ideal for karyotyping.

Q20. What happens during anaphase of mitosis?
Answer:
Centromeres split, and sister chromatids separate and move toward opposite poles, ensuring equal chromosome distribution.

Q21. Explain the events of telophase.
Answer:
Chromosomes reach poles, decondense into chromatin, nuclear membrane reforms, nucleolus reappears, and spindle fibers disappear.

Q22. Why is mitosis called equational division?
Answer:
It maintains the same chromosome number in parent and daughter cells.

Q23. Mention two biological roles of mitosis.
Answer:
Mitosis enables growth of multicellular organisms and repair or replacement of damaged tissues.

Q24. In which cells does mitosis occur?
Answer:
Mitosis occurs in somatic or body cells.

Q25. How does mitosis help in asexual reproduction?
Answer:
It produces genetically identical offspring without variation in some organisms.

Q26. What is the role of spindle fibers in mitosis?
Answer:
Spindle fibers help in alignment and separation of chromosomes during cell division.

Q27. What is meant by karyokinesis?
Answer:
Karyokinesis is the division of the nucleus during mitosis.

Q28. Why is mitosis essential for tissue repair?
Answer:
It replaces damaged or dead cells with new genetically identical cells.

Q29. What happens to chromosome number after mitosis?
Answer:
Chromosome number remains unchanged in daughter cells.

Q30. Which phase immediately follows mitosis?
Answer:
Cytokinesis immediately follows mitosis.

Section C: Meiosis (Q31–Q45)

Q31. Define meiosis.
Answer:
Meiosis is a reduction division producing four haploid daughter cells from a diploid parent cell.

Q32. Where does meiosis occur?
Answer:
Meiosis occurs in germ cells that produce gametes.

Q33. How many divisions occur in meiosis?
Answer:
Two successive divisions occur: meiosis I and meiosis II.

Q34. Why is meiosis I called reductional division?
Answer:
Because homologous chromosomes separate, reducing chromosome number to half.

Q35. Describe synapsis.
Answer:
Synapsis is the pairing of homologous chromosomes during zygotene stage of prophase I.

Q36. What is crossing over and why is it important?
Answer:
Crossing over is the exchange of genetic material between homologous chromosomes, leading to genetic variation.

Q37. In which stage does crossing over occur?
Answer:
Crossing over occurs during the pachytene stage of prophase I.

Q38. What are chiasmata?
Answer:
Chiasmata are visible points of crossing over between homologous chromatids.

Q39. What separates during anaphase I?
Answer:
Homologous chromosomes separate during anaphase I.

Q40. What separates during anaphase II?
Answer:
Sister chromatids separate during anaphase II.

Q41. How many daughter cells are formed after meiosis?
Answer:
Four haploid daughter cells are formed.

Q42. Why is meiosis essential for sexual reproduction?
Answer:
It produces haploid gametes and maintains chromosome number across generations.

Q43. How does meiosis generate variation?
Answer:
Through crossing over and independent assortment of chromosomes.

Q44. Which division resembles mitosis: meiosis I or meiosis II?
Answer:
Meiosis II resembles mitosis.

Q45. State one evolutionary significance of meiosis.
Answer:
It introduces genetic variation, promoting evolution.

Section D: Significance of Cell Division (Q46–Q50)

Q46. Why is cell division essential for growth?
Answer:
It increases the number of cells, enabling growth and development.

Q47. How does cell division help in repair and regeneration?
Answer:
It replaces damaged or dead cells with new functional cells.

Q48. Which division maintains chromosome number?
Answer:
Mitosis maintains chromosome number.

Q49. Which division reduces chromosome number?
Answer:
Meiosis reduces chromosome number by half.

Q50. Why is controlled cell division necessary?
Answer:
Uncontrolled cell division can cause abnormal growth and diseases such as cancer.

✅ Academic Relevance

✔ 100% NCERT aligned
✔ Ideal for CBSE Class 11 short answer questions
✔ Strong focus on concept clarity and exam-oriented answers