Q.1 Which phase of the cell cycle is primarily involved in cell growth and DNA replication preparation?
G1 phase
S phase
G2 phase
M phase
Explanation - G1 phase is the first gap phase of interphase where the cell grows and prepares for DNA synthesis. S phase is for DNA replication.
Correct answer is: G1 phase
Q.2 During which phase of the cell cycle does DNA replication occur?
G1 phase
S phase
G2 phase
M phase
Explanation - The S (Synthesis) phase is when DNA is replicated, ensuring that each daughter cell receives identical genetic material.
Correct answer is: S phase
Q.3 Which of the following checkpoints ensures DNA is completely replicated before mitosis?
G1 checkpoint
G2 checkpoint
M checkpoint
Spindle checkpoint
Explanation - The G2 checkpoint verifies DNA replication completeness and DNA integrity before allowing the cell to enter mitosis.
Correct answer is: G2 checkpoint
Q.4 Which protein complex is primarily responsible for initiating the M phase in eukaryotic cells?
Cyclin D-CDK4
Cyclin E-CDK2
Cyclin B-CDK1
Cyclin A-CDK2
Explanation - Cyclin B forms a complex with CDK1, which triggers the entry of the cell into mitosis.
Correct answer is: Cyclin B-CDK1
Q.5 During metaphase of mitosis, chromosomes align at which location?
Centrosome
Equatorial plate
Spindle pole
Nuclear envelope
Explanation - In metaphase, chromosomes align along the cell’s equatorial plane, also called the metaphase plate.
Correct answer is: Equatorial plate
Q.6 Which structure pulls sister chromatids apart during anaphase of mitosis?
Centrosome
Kinetochores
Spindle fibers
Chromatin
Explanation - Spindle fibers attach to kinetochores and pull sister chromatids to opposite poles during anaphase.
Correct answer is: Spindle fibers
Q.7 Which type of cell division reduces the chromosome number by half?
Mitosis
Meiosis I
Meiosis II
Binary fission
Explanation - Meiosis I is a reductional division where homologous chromosomes separate, reducing the chromosome number by half.
Correct answer is: Meiosis I
Q.8 Crossing over occurs during which phase of meiosis?
Prophase I
Metaphase I
Anaphase I
Telophase I
Explanation - During prophase I, homologous chromosomes pair up and exchange segments, increasing genetic variation.
Correct answer is: Prophase I
Q.9 Which phase of mitosis is characterized by the disappearance of the nuclear envelope?
Prophase
Metaphase
Anaphase
Telophase
Explanation - During prophase, chromatin condenses into chromosomes, and the nuclear envelope breaks down.
Correct answer is: Prophase
Q.10 Which term describes non-dividing cells that remain in G0 phase?
Stem cells
Senescent cells
Differentiated cells
Quiescent cells
Explanation - Cells in G0 phase exit the cell cycle and become metabolically active but do not divide; these are called quiescent cells.
Correct answer is: Quiescent cells
Q.11 Which enzyme is crucial for separating replicated sister chromatids during anaphase?
DNA polymerase
Topoisomerase
Cohesin
Separase
Explanation - Separase cleaves cohesin proteins holding sister chromatids together, allowing them to move to opposite poles.
Correct answer is: Separase
Q.12 Cytokinesis in animal cells is achieved by:
Cell wall formation
Cleavage furrow formation
Spindle fiber elongation
Chromosome condensation
Explanation - In animal cells, cytokinesis occurs via the formation of a cleavage furrow that pinches the cell into two daughter cells.
Correct answer is: Cleavage furrow formation
Q.13 Which of the following is NOT a phase of mitosis?
Prophase
Metaphase
Interphase
Telophase
Explanation - Interphase is a preparatory phase for mitosis, not part of the actual mitotic phases.
Correct answer is: Interphase
Q.14 During which phase of meiosis do homologous chromosomes separate?
Meiosis I
Meiosis II
Mitosis
G1 phase
Explanation - In meiosis I, homologous chromosomes separate, unlike meiosis II where sister chromatids separate.
Correct answer is: Meiosis I
Q.15 Which structure ensures proper segregation of chromosomes during cell division?
Centrosome
Lysosome
Ribosome
Endoplasmic reticulum
Explanation - The centrosome organizes spindle fibers that segregate chromosomes during mitosis and meiosis.
Correct answer is: Centrosome
Q.16 Which phase of mitosis is characterized by decondensation of chromosomes and formation of the nuclear envelope?
Prophase
Metaphase
Anaphase
Telophase
Explanation - In telophase, chromosomes decondense and the nuclear envelope reforms, marking the near end of mitosis.
Correct answer is: Telophase
Q.17 The spindle assembly checkpoint ensures that:
DNA is replicated
Chromosomes are attached to spindle fibers
Cell grows sufficiently
Cytokinesis occurs
Explanation - This checkpoint prevents anaphase from starting until all chromosomes are properly attached to the spindle, avoiding missegregation.
Correct answer is: Chromosomes are attached to spindle fibers
Q.18 In meiosis, independent assortment of chromosomes occurs during:
Prophase I
Metaphase I
Anaphase I
Telophase I
Explanation - During metaphase I, homologous chromosome pairs align randomly, resulting in independent assortment and genetic variation.
Correct answer is: Metaphase I
Q.19 Which type of cell division is used by prokaryotes?
Mitosis
Meiosis
Binary fission
Budding
Explanation - Prokaryotic cells divide by binary fission, a simpler process than mitosis or meiosis.
Correct answer is: Binary fission
Q.20 Which protein acts as a tumor suppressor and regulates the G1 checkpoint?
p53
Cyclin D
CDK2
Mdm2
Explanation - p53 monitors DNA damage and can halt the cell cycle at G1, allowing repair or inducing apoptosis if damage is severe.
Correct answer is: p53
Q.21 The longest phase of the cell cycle is typically:
M phase
G1 phase
S phase
G2 phase
Explanation - G1 is often the longest phase as the cell grows and synthesizes proteins and organelles necessary for DNA replication.
Correct answer is: G1 phase
Q.22 Synapsis of homologous chromosomes occurs during:
Prophase I of meiosis
Prophase II of meiosis
Prophase of mitosis
Metaphase I of meiosis
Explanation - Synapsis, the pairing of homologous chromosomes, occurs in prophase I and is crucial for crossing over.
Correct answer is: Prophase I of meiosis
Q.23 Which structure is absent in plant cells but present in animal cells during cytokinesis?
Cell plate
Cleavage furrow
Plasma membrane
Nucleus
Explanation - Animal cells undergo cytokinesis via cleavage furrow, while plant cells form a cell plate due to the rigid cell wall.
Correct answer is: Cleavage furrow
Q.24 Which of the following occurs during the G2 phase of the cell cycle?
DNA replication
Cell growth and organelle duplication
Chromosome alignment
Chromatid separation
Explanation - G2 phase involves final preparations for mitosis, including organelle duplication and repair of DNA.
Correct answer is: Cell growth and organelle duplication
Q.25 Homologous chromosomes pair up to form tetrads during which meiosis phase?
Prophase I
Metaphase I
Anaphase I
Telophase II
Explanation - During prophase I, homologous chromosomes synapse to form tetrads, allowing crossing over to occur.
Correct answer is: Prophase I