2nd Year NotesBiology class 12th

2nd Year Biology Chapter 21- Cell Cycle

2nd Year Biology Chapter 21- Cell Cycle Question and Answer

Short and Simple Question And Answer

Q 1. What is the cell cycle?

Ans. The cell cycle is a sequence of changes in a cell, including growth, DNA replication, and cell division.

Q 2. How long is the human cell cycle?

Ans. The average human cell cycle takes about 24 hours.

Q 3. What is chromatin?

Ans. Chromatin is a network of fine threads made visible with histologic stains of DNA.

Q 4. What do higher plants have instead of visible centrioles?

Ans. Higher plants have an analogous region from which spindle microtubules radiate.

Q 5. What is metastasis?

Ans. Metastasis is the spread of cancer cells to other parts of the body from their original site.

Q 6. When does meiosis occur in plants and animals?

Ans. Meiosis occurs in diploid cells during gamete formation in animals and when spores are produced in plants.

Q 7. Define crossing over?

Ans. Crossing over is the exchange of segments between non-sister chromatids of homologous chromosomes due to chiasmata formation.

Q 8. Name two significant events of meiosis?

Ans. Two significant events of meiosis are crossing over and random assortment of chromosomes.

Q 9. How many chromosomes are present in males affected by Klinefelter’s syndrome?

Ans. Males with Klinefelter’s syndrome can have 48 chromosomes (XXXY), 49 chromosomes (XXXY), or 47 chromosomes (XYY).

Q 10. What are the symptoms of Turner’s syndrome?

Ans. Symptoms of Turner’s syndrome include short stature, webbed neck, absence of ovaries, and a complete absence of germ cells in individuals with one missing X chromosome (45 chromosomes).

Q 11. What is apoptosis?

Ans. Apoptosis is the programmed sequence of events leading to cell self-destruction.

Q 12. Name the stages of interphase?

Ans. Interphase consists of G1-phase, S-phase, and G2-phase.

Q 13. What is G1-phase?

Ans. G1-phase is a period of metabolic activity, growth, and accumulation of DNA base units.

Q 14. What is G0?

Ans. G0 is a phase where post-mitotic cells exit the cell cycle and may remain without further proliferation.

Q 15. What happens in the S-phase of the cell cycle?

Ans. In the S-phase, DNA is synthesized, and the chromosome number doubles.

Q 16. What occurs in the G2-phase (pre-mitotic phase)?

Ans. In the G2-phase, the cell prepares for division by synthesizing energy, proteins, RNA, and microtubule subunits. Q 17. Define mitosis?

Ans. Mitosis is a type of cell division that ensures the same number of chromosomes in daughter cells as in the parent cells.

Q 18. What are the two conventional phases of Mitosis?

Ans. The two conventional phases of Mitosis are Karyokinesis (nucleus division) and Cytokinesis (whole cell division).

Q 19. What is the Mitotic apparatus?

Ans. The specialized microtubule structure, including asters and spindles, is called the Mitotic apparatus. Q 20. Name the microtubules originating from centrioles?

Ans. The microtubules originating from centrioles are astral microtubules, kinetochore microtubules, and polar microtubules.

Q 21. What happens in Prophase of mitosis?

Ans. Chromosomes become visible and nuclear changes occur.

Q 22. What is kinetochore?

Ans. A specialized region on the centromere.

Q 23. What occurs in Telophase of mitosis?

Ans. Chromosomes decondense, nuclear changes happen.

Q 24. What is Phragmoplast?

Ans. A membrane structure in plant cytokinesis.

Q 25. Define cancer?

Ans. Malignant growth from uncontrolled cell division.

Q 26. What is Tumour?

Ans. Uncontrolled cell proliferation forming a mass.

Q 27. What are two basic types of tumour?

Ans. Benign and Malignant.

Q 28. What is benign tumours?

Ans. Small, localized, behave like normal cells.

Q 29. What is malignant tumour?

Ans. Rapidly dividing, invasive, can spread.

Q 30. How to distinguish cancer cells from normal cells?

Ans. Less differentiated, rapid growth characteristics.

Q 31. What are the main causes of cancer?

Ans. Somatic cell mutations in cell division genes.

Q 32. Define meiosis?

Ans. Cell division reducing chromosome number.

Q 33. How does prophase of meiosis differ from mitosis?

Ans. Chromosomes behave as homologous pairs.

Q 34. What are homologous chromosomes?

Ans. Similar but not necessarily identical chromosomes.

Q 35. Name sub-stages of prophase I of meiosis?

Ans. Leptotene, zygotene, diplotene, diakinesis.

Q 36. What is synapsis?

Ans. Pairing of homologous chromosomes.

Q 37. What is bivalent or tetrad?

Ans. Paired homologous chromosomes.

Q 38. Duration of Pachytene, leptotene, zygotene?

Ans. Pachytene can last long, leptotene and zygotene are short.

Q 39. What is chiasmata?

Ans. Points of interchange in homologous chromosomes.

Q 40. What happens in Diakinesis?

Ans. Maximum chromosome condensation, separation.

Q 41. Events in metaphase I of meiosis?

Ans. Nuclear changes, spindle fibers, bivalent alignment.

Q 42. How does anaphase I of meiosis differ from mitosis?

Ans. Only homologous chromosomes separate.

Q 43. How does meiosis maintain constant chromosome number?

Ans. Halves chromosome number in gametes, restores after fertilization.

Q 44. Define non-disjunction?

Ans. Failure to segregate chromosomes in cell division.

Q 45. What is autosomal non-disjunction?

Ans. Failure of autosomal chromosomes to segregate.

Q 46. What is Downs Syndrome (Mongolism)?

Ans. Extra 21st chromosome, resulting in 47 chromosomes.

Q 47. Is Downs syndrome related to the mother’s age?

Ans. Yes, risk increases with mother’s age.

Q 48. What are symptoms of Downs syndrome?

Ans. Flat face, squint eyes, mental retardation.

Q 49. What is sex chromosomal non-disjunction?

Ans. Failure of sex chromosomes to segregate.

Q 50. What is Necrosis?

Ans. Cell death due to tissue damage.

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