Q31. Which of the following events occurs during interphase?
a) Chromosome condensation
b) Sister chromatids separate
c) DNA replication
d) Spindle fiber formation
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Correct Answer: c) DNA replication
Explanation: Interphase is the phase of the cell cycle where the cell prepares for division by undergoing growth and DNA replication. During this phase, the DNA is duplicated to ensure that each daughter cell receives a complete set of genetic material. Chromosome condensation, sister chromatid separation, and spindle fiber formation occur during mitosis and meiosis, not during interphase.
Q32. What is the consequence of nondisjunction during meiosis?
a) Production of gametes with an incorrect number of chromosomes
b) Formation of genetically identical daughter cells
c) Loss of genetic material during cell division
d) Premature initiation of anaphase
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Correct Answer: a) Production of gametes with an incorrect number of chromosomes
Explanation: Nondisjunction is a chromosomal abnormality that occurs when homologous chromosomes or sister chromatids fail to separate properly during meiosis. As a result, one daughter cell may receive an extra chromosome, while the other may lack a chromosome. This leads to the production of gametes with an incorrect number of chromosomes, which can result in genetic disorders such as Down syndrome.
Q33. Which of the following accurately describes the chromosome number in daughter cells produced by mitosis?
a) Diploid (2n)
b) Haploid (n)
c) Tetraploid (4n)
d) Triploid (3n)
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Correct Answer: a) Diploid (2n)
Explanation: Mitosis is a type of cell division that produces two daughter cells, each with the same chromosome number as the parent cell. Therefore, the chromosome number in daughter cells produced by mitosis is diploid (2n), meaning they contain the same number of chromosomes as the parent cell.
Q34. During which phase of the cell cycle does the cell grow and perform its normal functions?
a) G1 phase
b) S phase
c) G2 phase
d) M phase
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Correct Answer: a) G1 phase
Explanation: The G1 phase, or gap 1 phase, is the first phase of the cell cycle during which the cell grows and performs its normal functions. During this phase, the cell synthesizes proteins, grows in size, and carries out its metabolic activities in preparation for DNA replication in the subsequent S phase.
Q35. What is the primary function of the centrosome during cell division?
a) To regulate cell growth
b) To organize and assemble spindle fibers
c) To replicate DNA
d) To control cell differentiation
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Correct Answer: b) To organize and assemble spindle fibers
Explanation: The centrosome is an organelle involved in the organization and assembly of spindle fibers during cell division. It contains a pair of centrioles and serves as the microtubule organizing center (MTOC) from which spindle fibers emanate. Spindle fibers are essential for the movement and segregation of chromosomes during mitosis and meiosis.
Q36. Which of the following accurately describes the chromosome number in daughter cells produced by meiosis?
a) Diploid (2n)
b) Haploid (n)
c) Tetraploid (4n)
d) Triploid (3n)
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Correct Answer: b) Haploid (n)
Explanation: Meiosis is a type of cell division that reduces the chromosome number by half, resulting in the formation of haploid daughter cells. Therefore, the chromosome number in daughter cells produced by meiosis is haploid (n), meaning they contain half the number of chromosomes as the parent cell.
Q37. What is the significance of homologous chromosomes in meiosis?
a) They ensure the separation of sister chromatids during anaphase II.
b) They carry different versions of the same genes.
c) They prevent the attachment of spindle fibers to kinetochores.
d) They initiate the process of cytokinesis.
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Correct Answer: b) They carry different versions of the same genes.
Explanation: Homologous chromosomes are pairs of chromosomes that carry the same genes, but may have different versions (alleles) of those genes. During meiosis, homologous chromosomes undergo synapsis and crossing over, leading to the exchange of genetic material between chromatids. This process increases genetic diversity among offspring by reshuffling genetic combinations.
Q38. What is the role of the kinetochore during cell division?
a) To organize and assemble spindle fibers
b) To replicate DNA
c) To regulate cell growth
d) To initiate the process of cytokinesis
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Correct Answer: a) To organize and assemble spindle fibers
Explanation: The kinetochore is a protein structure located at the centromere of each chromosome. Its primary role is to attach to spindle fibers and facilitate the movement of chromosomes during cell division. By interacting with microtubules of the spindle apparatus, the kinetochore helps to organize and guide chromosome segregation during mitosis and meiosis.
Q39. What happens during cytokinesis in animal cells?
a) A cell plate forms between daughter cells.
b) The cell divides into two daughter cells.
c) The nuclear envelope reforms around separated chromosomes.
d) Chromosomes align along the equatorial plane.
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Correct Answer: b) The cell divides into two daughter cells.
Explanation: Cytokinesis is the final stage of the cell cycle during which the cytoplasm and organelles divide, resulting in the formation of two separate daughter cells. In animal cells, cytokinesis is achieved by the formation of a cleavage furrow, which gradually deepens and eventually pinches the parent cell into two daughter cells.
Q40. What is the consequence of a mutation in a tumor suppressor gene?
a) Uncontrolled cell division and tumor formation
b) Inhibition of cell growth and proliferation
c) Initiation of apoptosis (cell death)
d) Repair of DNA damage
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Correct Answer: a) Uncontrolled cell division and tumor formation
Explanation: Tumor suppressor genes encode proteins that regulate cell growth, proliferation, and apoptosis. Mutations in tumor suppressor genes can disrupt these regulatory functions, leading to uncontrolled cell division and tumor formation. Loss of tumor suppressor function removes the normal checks and balances on cell growth, allowing abnormal cells to proliferate unchecked.