Q41. What is the function of cyclins in the cell cycle?
a) To inhibit the progression of the cell cycle
b) To regulate the activity of cyclin-dependent kinases (CDKs)
c) To prevent DNA replication
d) To induce apoptosis
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Correct Answer: b) To regulate the activity of cyclin-dependent kinases (CDKs)
Explanation: Cyclins are proteins that bind to and activate cyclin-dependent kinases (CDKs), which are enzymes that control the progression of the cell cycle. Different cyclins are synthesized and degraded at specific points in the cell cycle, and their binding to CDKs helps regulate key events such as DNA replication, chromosome condensation, and mitotic spindle formation.
Q42. Which of the following is a characteristic of aneuploidy?
a) The presence of an extra set of chromosomes
b) Loss of one or more chromosomes
c) An abnormal number of chromosomes
d) Presence of only one copy of each chromosome
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Correct Answer: c) An abnormal number of chromosomes
Explanation: Aneuploidy is a chromosomal abnormality characterized by an abnormal number of chromosomes, which may involve the presence of an extra chromosome (trisomy) or the loss of a chromosome (monosomy). This imbalance in chromosome number can lead to genetic disorders and developmental abnormalities, such as Down syndrome (trisomy 21) or Turner syndrome (monosomy X).
Q43. What is the function of the mitotic spindle during mitosis?
a) To replicate DNA
b) To separate homologous chromosomes
c) To organize and segregate chromosomes
d) To initiate the process of cytokinesis
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Correct Answer: c) To organize and segregate chromosomes
Explanation: The mitotic spindle is a microtubule-based structure that forms during mitosis and is responsible for organizing and segregating chromosomes. It ensures that replicated chromosomes are properly aligned and segregated into two daughter cells during cell division. The spindle fibers attach to kinetochores on the chromosomes and exert forces that move the chromosomes to opposite poles of the cell.
Q44. What is the function of the G2 checkpoint in the cell cycle?
a) To ensure that DNA replication has been completed accurately
b) To monitor cell size and nutrient availability
c) To prevent the initiation of mitosis if DNA damage is detected
d) To regulate the activity of cyclin-dependent kinases (CDKs)
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Correct Answer: a) To ensure that DNA replication has been completed accurately
Explanation: The G2 checkpoint is a regulatory mechanism in the cell cycle that ensures DNA replication has been completed accurately before the cell enters mitosis. It monitors DNA integrity and repair processes, and if DNA damage or replication errors are detected, the checkpoint delays progression into mitosis until the damage is repaired or the errors are corrected.
Q45. What is the function of the metaphase plate during mitosis?
a) To ensure proper alignment of chromosomes
b) To initiate the condensation of chromosomes
c) To organize and assemble spindle fibers
d) To separate sister chromatids
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Correct Answer: a) To ensure proper alignment of chromosomes
Explanation: The metaphase plate, also known as the equatorial plane, is an imaginary plane located at the center of the cell during metaphase of mitosis. Its primary function is to ensure the proper alignment of chromosomes before their separation during anaphase. Chromosomes align along the metaphase plate with their centromeres oriented toward opposite poles of the cell, ensuring equal distribution of genetic material to the daughter cells.
Q46. Which of the following accurately describes the outcome of meiosis II?
a) Separation of homologous chromosomes
b) Production of genetically identical daughter cells
c) Reduction of chromosome number from diploid to haploid
d) Formation of a tetrad
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Correct Answer: c) Reduction of chromosome number from diploid to haploid
Explanation: Meiosis II follows meiosis I and involves the separation of sister chromatids, resulting in the formation of haploid daughter cells. This process reduces the chromosome number from diploid (2n) to haploid (n) and ensures genetic diversity among gametes.
Q47. What is the significance of genetic recombination during meiosis?
a) It ensures the separation of homologous chromosomes during anaphase I.
b) It prevents the attachment of spindle fibers to kinetochores.
c) It increases genetic diversity among offspring.
d) It initiates the process of cytokinesis.
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Correct Answer: c) It increases genetic diversity among offspring.
Explanation: Genetic recombination, which occurs during crossing over in prophase I of meiosis, involves the exchange of genetic material between homologous chromosomes. This process results in new combinations of alleles on chromosomes, increasing genetic diversity among offspring. It contributes to variations in traits within populations and enhances evolutionary potential.
Q48. Which of the following is a characteristic of sexual reproduction?
a) Involves the fusion of gametes from two parents
b) Results in the production of genetically identical offspring
c) Occurs only in unicellular organisms
d) Requires only one parent organism
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Correct Answer: a) Involves the fusion of gametes from two parents
Explanation: Sexual reproduction involves the fusion of gametes (sperm and egg cells) from two parent organisms to produce offspring with genetic contributions from both parents. This process leads to genetic diversity among offspring due to recombination and random assortment of chromosomes during meiosis.
Q49. What is the primary function of homologous chromosomes during meiosis?
a) To ensure the separation of sister chromatids during anaphase II
b) To carry different versions of the same genes
c) To form a tetrad during prophase I
d) To initiate the process of cytokinesis
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Correct Answer: c) To form a tetrad during prophase I
Explanation: Homologous chromosomes pair up during prophase I of meiosis to form structures called tetrads (or bivalents). This pairing allows for genetic recombination through crossing over, which results in the exchange of genetic material between chromatids. Homologous chromosomes carry the same genes in the same order but may have different alleles, contributing to genetic diversity among offspring.
Q50. Which of the following events occurs during telophase of mitosis?
a) Chromosomes align along the equatorial plane of the cell
b) Sister chromatids separate and move towards opposite poles
c) Nuclear envelope reforms around the separated chromosomes
d) Spindle fibers begin to disassemble
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Correct Answer: c) Nuclear envelope reforms around the separated chromosomes
Explanation: Telophase is the final stage of mitosis where the nuclear envelope reassembles around the separated sets of chromosomes. This process marks the completion of nuclear division and precedes cytokinesis, the division of the cytoplasm, resulting in the formation of two daughter cells.