During which phase of mitosis do chromosomes condense and become visible?
a) Interphase
b) Prophase
c) Metaphase
d) Anaphase
e) Telophase
Rationale: Prophase is the initial phase of mitosis where chromatin condenses into visible chromosomes. This condensation facilitates the separation of genetic material into daughter cells. Understanding this phase is crucial for comprehending the initiation of mitotic division.
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What structure holds the sister chromatids together during mitosis?
a) Centrosome
b) Centriole
c) Centromere
d) Spindle fiber
e) Nuclear membrane
Rationale: The centromere is the region of a chromosome where the sister chromatids are attached and held together. This attachment ensures proper alignment and distribution of genetic material during cell division, making it a pivotal structure in mitosis.
Which phase of mitosis involves the alignment of chromosomes along the cell’s equator?
a) Prophase
b) Metaphase
c) Anaphase
d) Telophase
e) Cytokinesis
Rationale: Metaphase is characterized by the alignment of chromosomes at the cell’s equatorial plane. This alignment ensures that each daughter cell receives an equal and complete set of chromosomes, maintaining genomic integrity during cell division.
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What event marks the beginning of anaphase in mitosis?
a) Disappearance of the nuclear envelope
b) Condensation of chromosomes
c) Separation of sister chromatids
d) Alignment of chromosomes at the equator
e) Formation of the mitotic spindle
Rationale: Anaphase begins with the separation of sister chromatids, which are pulled toward opposite poles of the cell by the spindle fibers. This crucial event ensures the accurate distribution of genetic material to daughter cells during mitotic division.
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Which structure is responsible for organizing and separating the chromosomes during mitosis?
a) Nucleolus
b) Golgi apparatus
c) Endoplasmic reticulum
d) Centrosome
e) Lysosome
Rationale: The centrosome plays a central role in organizing and separating chromosomes during mitosis by forming the mitotic spindle. This spindle apparatus ensures proper chromosome alignment and segregation, essential for the accurate distribution of genetic material to daughter cells.
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What is the result of telophase in mitosis?
a) Chromosome condensation
b) Nuclear envelope formation
c) Sister chromatid separation
d) Chromosome alignment
e) Cytokinesis
Rationale: Telophase marks the end of mitosis, during which the nuclear envelope reforms around the separated chromosomes in each daughter cell. This reformation of the nuclear envelope restores the compartmentalization of genetic material, preparing the cells for their subsequent functions.
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Which of the following accurately describes cytokinesis?
a) Division of the cytoplasm
b) Separation of sister chromatids
c) Alignment of chromosomes at the equator
d) Condensation of chromosomes
e) Formation of the mitotic spindle
Rationale: Cytokinesis is the process of dividing the cytoplasm to form two distinct daughter cells following mitosis. This division ensures that each daughter cell receives its own set of organelles and cellular components, completing the cell division process.
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What is the primary function of mitosis in multicellular organisms?
a) Reproduction
b) Growth
c) DNA repair
d) Energy production
e) Waste elimination
Rationale: Mitosis primarily contributes to the growth of multicellular organisms by producing new cells to replace old or damaged ones. Through mitotic division, cells proliferate and differentiate to form tissues and organs, facilitating overall organismal growth and development.
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Which phase of the cell cycle is characterized by DNA replication?
a) G1 phase
b) S phase
c) G2 phase
d) M phase
e) G0 phase
Rationale: The S phase of the cell cycle is dedicated to DNA replication, during which the genetic material is duplicated to ensure each daughter cell receives a complete set of chromosomes. Understanding this phase is essential for grasping the continuity of genetic information during cell division.
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What is the significance of mitosis in tissue repair?
a) It generates genetic diversity
b) It removes damaged cells
c) It replaces lost or damaged cells
d) It produces energy for cell metabolism
e) It eliminates waste products
Rationale: Mitosis plays a crucial role in tissue repair by replacing lost or damaged cells with new ones. This process ensures the restoration of tissue integrity and functionality, contributing to the organism’s overall health and homeostasis.
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Which checkpoint in the cell cycle ensures that DNA replication is complete and undamaged before proceeding to mitosis?
a) G1 checkpoint
b) S checkpoint
c) G2 checkpoint
d) M checkpoint
e) G0 checkpoint
Rationale: The G2 checkpoint ensures that DNA replication is complete and accurate, and any DNA damage is repaired before the cell enters mitosis. This checkpoint plays a crucial role in maintaining genomic stability and preventing the transmission of genetic errors to daughter cells.
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What is the role of cyclin-dependent kinases (CDKs) in regulating the cell cycle?
a) Initiating DNA replication
b) Repairing DNA damage
c) Regulating progression through cell cycle phases
d) Promoting cell differentiation
e) Inducing apoptosis
Rationale: Cyclin-dependent kinases (CDKs) are enzymes that regulate the cell cycle by phosphorylating target proteins involved in cell cycle progression. Their activity is tightly controlled by cyclins, which fluctuate in concentration throughout the cell cycle, ensuring orderly progression through each phase.
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What is the consequence of a defect in the spindle checkpoint during mitosis?
a) Unequal distribution of chromosomes
b) Failure of cytokinesis
c) Premature entry into S phase
d) Arrest in G1 phase
e) Inability to replicate DNA
Rationale: The spindle checkpoint monitors the attachment of spindle fibers to kinetochores and ensures that chromosomes are properly aligned before proceeding to anaphase. A defect in this checkpoint can lead to unequal distribution of chromosomes, resulting in aneuploidy and genetic instability.
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Which phase of mitosis is characterized by the reformation of the nuclear envelope and decondensation of chromosomes?
a) Prophase
b) Metaphase
c) Anaphase
d) Telophase
e) Interphase
Rationale: Telophase marks the final stage of mitosis, during which the nuclear envelope reassembles around the separated chromosomes, and the chromatin decondenses. This process prepares the daughter cells for their respective functions in the interphase.
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What is the function of the mitotic spindle during mitosis?
a) Separating sister chromatids
b) Condensing chromosomes
c) Forming the nuclear envelope
d) Initiating DNA replication
e) Facilitating cytokinesis
Rationale: The mitotic spindle is responsible for separating sister chromatids and ensuring that each daughter cell receives an accurate and complete set of chromosomes. Its dynamic structure and motor proteins exert forces to move chromosomes to opposite poles during mitotic division.