The Most Comprehensive Question Bank for ICSE Class 10 Students
Multiple Choice Questions (MCQs)
1. What is the main purpose of the G1 phase in the cell cycle?
(a) DNA replication
(b) Protein synthesis
(c) Cell growth
(d) Chromosome segregation
Answer: (c) Cell growth
Explanation: The G1 phase, part of Interphase, is primarily focused on cell growth and preparation for DNA replication in the S phase.
2. During which phase of mitosis do chromosomes align at the cell’s equator?
(a) Prophase
(b) Metaphase
(c) Anaphase
(d) Telophase
Answer: (b) Metaphase
Explanation: During metaphase, chromosomes align at the cell’s equator, preparing for segregation into daughter cells.
3. Which of the following is a characteristic feature of meiosis but not mitosis?
(a) Chromosome replication
(b) Two cell divisions
(c) Formation of identical cells
(d) Spindle formation
Answer: (b) Two cell divisions
Explanation: Meiosis includes two rounds of cell division (meiosis I and II), unlike mitosis, which only has one.
4. Homologous chromosomes pair up during which stage of meiosis?
(a) Prophase I
(b) Metaphase I
(c) Anaphase I
(d) Telophase I
Answer: (a) Prophase I
Explanation: During Prophase I of meiosis, homologous chromosomes pair up, a process known as synapsis.
5. What is the primary significance of crossing over in meiosis?
(a) DNA replication
(b) Cell division
(c) Genetic variation
(d) Chromosome alignment
Answer: (c) Genetic variation
Explanation: Crossing over, which occurs during Prophase I of meiosis, leads to genetic variation by exchanging genetic material between homologous chromosomes.
6. Which structure holds the sister chromatids together?
(a) Centriole
(b) Spindle fiber
(c) Centromere
(d) Nucleosome
Answer: (c) Centromere
Explanation: The centromere is the region where sister chromatids are held together until they are separated during cell division.
7. In the context of DNA structure, what are nucleosomes?
(a) DNA segments
(b) DNA and RNA
(c) DNA and proteins
(d) RNA only
Answer: (c) DNA and proteins
Explanation: Nucleosomes are structural units of a chromosome, consisting of a segment of DNA wound around a core of histone proteins.
8. How many chromosomes are present in a human somatic cell during the G1 phase?
(a) 23
(b) 46
(c) 92
(d) 69
Answer: (b) 46
Explanation: Human somatic cells in the G1 phase of the cell cycle have 46 chromosomes, which is the diploid number.
9. During which phase of the cell cycle does DNA replication occur?
(a) G1 phase
(b) S phase
(c) G2 phase
(d) M phase
Answer: (b) S phase
Explanation: DNA replication occurs during the S (synthesis) phase of the cell cycle.
10. What is the end result of meiosis in terms of the chromosome number in daughter cells?
(a) Doubled
(b) Unchanged
(c) Halved
(d) Tripled
Answer: (c) Halved
Explanation: Meiosis reduces the chromosome number by half in daughter cells, producing haploid cells from diploid ones.
11. What occurs during the G2 phase of the cell cycle?
(a) DNA replication
(b) Cell growth and preparation for mitosis
(c) Division of cytoplasm
(d) Separation of sister chromatids
Answer: (b) Cell growth and preparation for mitosis
Explanation: The G2 phase involves further cell growth and preparation for the division of the nucleus (mitosis).
12. In which stage of mitosis do the nuclear membrane and nucleolus disappear?
(a) Prophase
(b) Metaphase
(c) Anaphase
(d) Telophase
Answer: (a) Prophase
Explanation: During prophase, the nuclear membrane and nucleolus disintegrate, and chromosomes become visible.
13. Which of the following statements about chromatin is true?
(a) It is visible only during cell division
(b) It consists solely of DNA
(c) It is the relaxed form of DNA present during interphase
(d) It is made up of only proteins
Answer: (c) It is the relaxed form of DNA present during interphase
Explanation: Chromatin is the less condensed form of genetic material (DNA and proteins) present during the interphase.
14. During which phase of meiosis does independent assortment of chromosomes occur?
(a) Prophase I
(b) Metaphase I
(c) Anaphase I
(d) Telophase I
Answer: (b) Metaphase I
Explanation: Independent assortment occurs during Metaphase I, where homologous chromosomes line up randomly at the equatorial plate.
15. Which of the following is not a component of a nucleotide?
(a) Phosphate group
(b) Ribose sugar
(c) Nitrogenous base
(d) Histone protein
Answer: (d) Histone protein
Explanation: A nucleotide is made up of a phosphate group, a sugar (ribose in RNA, deoxyribose in DNA), and a nitrogenous base. Histone proteins are not part of nucleotides.
16. What is the primary function of mitosis in multicellular organisms?
(a) Sexual reproduction
(b) Growth and tissue repair
(c) Production of gametes
(d) Genetic variation
Answer: (b) Growth and tissue repair
Explanation: Mitosis in multicellular organisms primarily functions in growth, development, and repair of tissues.
17. In meiosis, when does crossing over occur?
(a) Prophase I
(b) Anaphase I
(c) Metaphase II
(d) Telophase II
Answer: (a) Prophase I
Explanation: Crossing over, the exchange of genetic material between non-sister chromatids, occurs during Prophase I of meiosis.
18. Which phase follows telophase in the cell cycle?
(a) Interphase
(b) Prophase
(c) Metaphase
(d) Cytokinesis
Answer: (d) Cytokinesis
Explanation: Cytokinesis, the division of the cytoplasm to form two separate daughter cells, typically follows telophase.
19. Which type of cell division results in four non-identical daughter cells?
(a) Binary fission
(b) Mitosis
(c) Meiosis
(d) Budding
Answer: (c) Meiosis
Explanation: Meiosis results in four genetically diverse (non-identical) haploid daughter cells.
20. What is the main difference between sister and non-sister chromatids?
(a) Sister chromatids are identical, while non-sister chromatids are not
(b) Sister chromatids are found in different cells, while non-sister chromatids are in the same cell
(c) Sister chromatids contain RNA, while non-sister chromatids contain DNA
(d) Sister chromatids are involved in mitosis, while non-sister chromatids participate in meiosis
Answer: (a) Sister chromatids are identical, while non-sister chromatids are not identical.
Explanation: Sister chromatids are identical.
21. Which of the following best describes a centrosome?
(a) A structure that synthesizes proteins
(b) A region organizing the cell’s microtubules
(c) A part of the chromosome carrying genetic information
(d) A component of the cell membrane
Answer: (b) A region organizing the cell’s microtubules
Explanation: The centrosome is a region in animal cells that serves as the main microtubule organizing center, particularly important during cell division.
22. What happens during anaphase of mitosis?
(a) Chromosomes condense
(b) Chromosomes align at the cell’s equator
(c) Sister chromatids separate and move to opposite poles
(d) Nuclear membrane reforms
Answer: (c) Sister chromatids separate and move to opposite poles
Explanation: During anaphase, the sister chromatids of each chromosome separate and are pulled to opposite poles of the cell.
23. What is a karyotype?
(a) A type of cell division
(b) A structure within the cell nucleus
(c) The physical appearance of a cell
(d) An organized profile of an individual’s chromosomes
Answer: (d) An organized profile of an individual’s chromosomes
Explanation: A karyotype is an organized profile of an individual’s chromosomes, arranged and photographed according to size, shape, and number.
24. What is the primary role of spindle fibers during cell division?
(a) DNA replication
(b) Cell growth
(c) Movement of chromosomes
(d) Protein synthesis
Answer: (c) Movement of chromosomes
Explanation: Spindle fibers are essential for the movement and proper segregation of chromosomes during both mitosis and meiosis.
25. Which phase of mitosis is characterized by the formation of two new nuclei?
(a) Prophase
(b) Metaphase
(c) Anaphase
(d) Telophase
Answer: (d) Telophase
Explanation: During telophase, the chromosomes reach the poles of the cell, and the nuclear membrane starts to reform, resulting in the formation of two new nuclei.
26. What is the function of histones in a cell?
(a) They aid in cell movement
(b) They package and order the DNA into structural units
(c) They synthesize proteins
(d) They assist in cell-to-cell communication
Answer: (b) They package and order the DNA into structural units
Explanation: Histones are proteins that play a critical role in packaging DNA into nucleosomes, thereby organizing it within the nucleus.
27. During which stage of cell division do chromosomes first become visible under a light microscope?
(a) Interphase
(b) Prophase
(c) Anaphase
(d) Telophase
Answer: (b) Prophase
Explanation: Chromosomes become visible under a light microscope during prophase, as the chromatin condenses.
28. In the cell cycle, the DNA content of a cell is duplicated during:
(a) G1 phase
(b) S phase
(c) G2 phase
(d) M phase
Answer: (b) S phase
Explanation: The S phase (Synthesis phase) of the cell cycle is where DNA replication occurs, resulting in the duplication of DNA content.
29. Homologous chromosomes separate during which process?
(a) Mitosis
(b) Meiosis I
(c) Meiosis II
(d) Cytokinesis
Answer: (b) Meiosis I
Explanation: During Meiosis I, homologous chromosomes (each consisting of two sister chromatids) separate and move to different cells.
30. Which of the following is a feature of plant cell division that distinguishes it from animal cell division?
(a) Formation of a cell plate
(b) The presence of a spindle apparatus
(c) Chromosome replication
(d) Formation of a cleavage furrow
Answer: (a) Formation of a cell plate
Explanation: In plant cells, a cell plate forms during cytokinesis to divide the cell into two, unlike the cleavage furrow in animal cells.
31. During cell division, what is the role of the centromere?
(a) It synthesizes DNA.
(b) It attaches the cell to the spindle fibers.
(c) It replicates the cell’s organelles.
(d) It produces ribosomal RNA.
Answer: (b) It attaches the cell to the spindle fibers.
Explanation: The centromere is the region on a chromosome that attaches to spindle fibers during cell division, ensuring proper segregation of chromosomes.
32. Which process is specifically associated with the production of gametes?
(a) Mitosis
(b) Meiosis
(c) Binary fission
(d) Budding
Answer: (b) Meiosis
Explanation: Meiosis is the cell division process that leads to the formation of gametes (sperm and egg cells) with half the number of chromosomes compared to somatic cells.
33. What is the primary outcome of the synthesis (S) phase in the cell cycle?
(a) Cell growth
(b) Duplication of DNA
(c) Protein synthesis
(d) Division of the nucleus
Answer: (b) Duplication of DNA
Explanation: The primary outcome of the S phase in the cell cycle is the duplication of the cell’s DNA in preparation for cell division.
34. Which of the following terms refers to the programmed death of cells?
(a) Necrosis
(b) Apoptosis
(c) Cytolysis
(d) Autophagy
Answer: (b) Apoptosis
Explanation: Apoptosis is the process of programmed cell death, which is a regulated and controlled way cells can die to maintain health and homeostasis in an organism.
35. In the context of chromosomes, what are telomeres?
(a) The central part of a chromosome
(b) Repeating nucleotide sequences at the ends of chromosomes
(c) Sites where crossing over occurs
(d) The attachment points for spindle fibers
Answer: (b) Repeating nucleotide sequences at the ends of chromosomes
Explanation: Telomeres are the repetitive nucleotide sequences found at the ends of chromosomes, protecting the chromosome from deterioration or fusion with neighboring chromosomes.
36. Which of the following is not a phase of mitosis?
(a) Interphase
(b) Prophase
(c) Metaphase
(d) Anaphase
Answer: (a) Interphase
Explanation: Interphase is not a phase of mitosis but a part of the cell cycle where the cell prepares for division, occurring before mitosis.
37. What is the outcome of cytokinesis in animal cells?
(a) Formation of a cell wall
(b) Duplication of DNA
(c) Division of the cytoplasm into two daughter cells
(d) Spindle formation
Answer: (c) Division of the cytoplasm into two daughter cells
Explanation: Cytokinesis in animal cells results in the division of the cytoplasm, creating two separate daughter cells.
38. During which stage of meiosis does synapsis and the formation of tetrads occur?
(a) Prophase I
(b) Metaphase I
(c) Anaphase I
(d) Telophase I
Answer: (a) Prophase I
Explanation: Synapsis, the pairing of homologous chromosomes, and the formation of tetrads occur during Prophase I of meiosis.
39. What is the main difference between the products of mitosis and meiosis?
(a) Mitosis results in two diploid cells, while meiosis results in four haploid cells.
(b) Mitosis results in four diploid cells, while meiosis results in two haploid cells.
(c) Mitosis results in identical cells, while meiosis results in different cells.
(d) Both a and c are correct.
Answer: (d) Both a and c are correct.
Explanation: Mitosis results in two genetically identical diploid daughter cells, while meiosis results in four genetically diverse haploid cells.
40. Which organelle plays a crucial role in cell division in animal cells but is absent in plant cells?
(a) Golgi apparatus
(b) Centrioles
(c) Chloroplast
(d) Mitochondria
Answer: (b) Centrioles
Explanation: Centrioles play a crucial role in the formation of spindle fibers in animal cells during cell division but are absent in most plant cells.
41. What is the term for the phase in the cell cycle when the cell is performing its regular functions and not engaged in cell division?
(a) Mitotic phase
(b) Interphase
(c) Prophase
(d) Cytokinesis
Answer: (b) Interphase
Explanation: Interphase is the period during the cell cycle when the cell is not dividing but is involved in its regular metabolic activities and preparation for cell division.
42. Which event is not associated with prophase in mitosis?
(a) Condensation of chromatin into visible chromosomes
(b) Breakdown of the nuclear envelope
(c) Separation of sister chromatids
(d) Formation of the mitotic spindle
Answer: (c) Separation of sister chromatids
Explanation: The separation of sister chromatids occurs during anaphase, not prophase. Prophase is characterized by chromatin condensation, the breakdown of the nuclear envelope, and spindle formation.
43. In meiosis, genetic variation is introduced through which processes?
(a) Mitotic spindle formation and cytokinesis
(b) DNA replication and chromatin condensation
(c) Independent assortment and crossing over
(d) Nuclear envelope breakdown and telophase events
Answer: (c) Independent assortment and crossing over
Explanation: Independent assortment (during Metaphase I) and crossing over (during Prophase I) are key processes in meiosis that contribute to genetic variation.
44. Which of these structures is involved in protein synthesis?
(a) Centromere
(b) Chromatid
(c) Ribosome
(d) Spindle fiber
Answer: (c) Ribosome
Explanation: Ribosomes are cellular structures involved in synthesizing proteins from amino acids.
45. What is the end product of DNA replication in the S phase of the cell cycle?
(a) Two identical DNA molecules
(b) Four identical DNA molecules
(c) Two different DNA molecules
(d) One single-stranded DNA molecule
Answer: (a) Two identical DNA molecules
Explanation: During the S phase, DNA replication results in two identical DNA molecules, each consisting of one old and one new strand (semi-conservative replication).
46. Which of the following best defines a gene?
(a) A segment of DNA that encodes for a protein
(b) A type of chromosome
(c) A phase in cell division
(d) A structure within the nucleus
Answer: (a) A segment of DNA that encodes for a protein
Explanation: A gene is a unit of heredity and is a sequence of nucleotides in DNA that encodes the synthesis of a gene product, usually a protein.
47. During cell division, what function does the metaphase checkpoint perform?
(a) Ensures all chromosomes are replicated
(b) Checks if all chromosomes are properly attached to the spindle
(c) Determines if the cell has enough resources to divide
(d) Verifies the completion of cytokinesis
Answer: (b) Checks if all chromosomes are properly attached to the spindle
Explanation: The metaphase checkpoint ensures that all chromosomes are properly attached to the spindle apparatus to avoid chromosome missegregation.
48. What happens during telophase in mitosis?
(a) Chromosomes line up at the cell’s equator
(b) The nuclear membrane begins to reform around the separated chromosomes
(c) Chromosomes are replicated
(d) The cell grows in size
Answer: (b) The nuclear membrane begins to reform around the separated chromosomes
Explanation: During telophase, the nuclear membranes reform around each set of separated chromosomes, marking the end of nuclear division.
49. Which enzyme is primarily responsible for unzipping the DNA double helix during replication?
(a) DNA polymerase
(b) Helicase
(c) Ligase
(d) Topoisomerase
Answer: (b) Helicase
Explanation: Helicase is the enzyme responsible for unwinding and unzipping the DNA double helix by breaking the hydrogen bonds between the nucleotide base pairs.
50. In which phase of mitosis do the centromeres split and the sister chromatids separate?
(a) Prophase
(b) Metaphase
(c) Anaphase
(d) Telophase
Answer: (c) Anaphase
Explanation: During anaphase, the centromeres split, and the sister chromatids are pulled apart to opposite poles of the cell, becoming individual chromosomes.