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Cell is the smallest and the most fundamental structural and functional unit of all organisms and life. And like all living organisms, it undergoes cell division to increase the number of the cells and ensure the growth of the organisms. The cell cycle is the systemic step-wise process of cell division, and it is divided into two phases. Cell division in all the organisms is of mainly two types, that is meiosis and mitosis.
Cell Division
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Cell cycle and Phases
Cell division includes the multiplication of cells, which results in the formation of two daughter cells from one mother cell. The cell cycle is the stepwise sequence that is followed to ensure the division of the cell. The cell cycle usually prolongs for 24 hours in the case of eukaryotic organisms and comprises two phases.
- Interphase: Resting phase
- The M Phase: Cell division phase
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MCQs On Cell Cycle and Cell Division
Ques 1: Which phase, out of the following phases, has most of the events occurring in it?
- G1 Phase
- G2 Phase
- M Phase
- Anaphase
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Ans: c. M phase
Explanation: The M phase has most of the events occurring in it since it comprises four stages in karyokinesis (prophase, metaphase, anaphase, and telophase) followed by cytokinesis. This phase is characterized by all the key points involved in cell division and the formation of daughter cells.
Ques 2: Which of the following phases occupy 95% of the time involved in the cell cycle?
- Interphase
- Karyokinesis
- Metaphase
- Anaphase
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Ans: a. Interphase
Explanation: The cell cycle is broadly composed of two phases, the interphase, and the M phase. Interphase occupies most of the period when the cell is involved in the cell cycle. It occupies 95% of the period, during which the cell prepares itself for the further processes involved in the cell division.
Ques 3: What is the G0 phase?
- Gap phase
- Growth Phase
- Gestational phase
- Quiescent phase
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Ans: d. Quiescent phase
Explanation: Some cells do not show cell division, and they enter into an inactive state after the gap one phase, this inactive phase is known as the quiescent phase or the G0 phase Cells in this stage remain metabolically active but no longer proliferate unless called on to do so depending on the requirement of the organism.
Ques 4: The alignment of the chromosomes in a straight line in the first phase of the M phase is called:
- Metaphase plate
- Cell plate
- Chromosome plate
- Anaphase plate
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Ans: a. Metaphase plate
Explanation: The plane of alignment of the chromosomes at metaphase is referred to as the metaphase plate. Cell-plate on the other hand represents the middle lamella between the walls of two adjacent plant cells, which further proceed to the division of the cell.
Ques 5: Which of the following phases is characterized by the gradual visibility of the chromosomes under a light microscope?
- Leptotene
- Zygotene
- Pachytene
- Diplotene
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Ans: a. Leptotene
Explanation: Prophase 1 in meiosis is complex and is divided into further five phases, Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis. Out of these five phases, during the leptotene stage, the chromosomes become gradually visible under the light microscope.
Ques 6: Which of the following phases is characterized by the dissolution of the synaptonemal complex?
- Zygotene
- Leptotene
- Pachytene
- Diplotene
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Ans: d. Diplotene
Explanation: The beginning of the diplotene phase is marked by the decomposition and dissolution of the synaptonemal complex and the habitual property of the recombined homologous (similar) chromosomes of the bivalents to differentiate from each other but not at the sites of crossovers.
Ques 7: What is the complex formed by a pair of synapsed homologous chromosomes known as?
- Bivalent
- Tetrad
- Both a and b
- None of the above
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Ans: c. Both a and b
Explanation: The electron micrographs of the stage zygotene show that the chromosome synapsis is accompanied by the formation of a complex structure called the synaptonemal complex. The complex structure formed by a pair of synapsed chromosomes that are similar in nature is called a bivalent or a tetrad.
Ques 8: The X-shaped crossovers in the diplotene stage are known as:
- Chiasmata
- Chiassmata
- Charita
- bivalent
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Ans: a. Chiasmata
Explanation: The diplotene phase is characterized by the dissolution of the synaptonemal complex and the separation of the recombined homologous chromosomes of the bivalents from each other except at the sites of crossovers. These X-shaped structures are called chiasmata.
Ques 9: Which of the following structural units can be seen in the prophase except?
- disintegrating nuclear membrane
- Asters
- Chromatin fibers
- Golgi apparatus
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Ans: d. Golgi apparatus
Explanation: The prophase is characterized by a loss of Golgi complexes, endoplasmic reticulum, nucleolus, and the nuclear envelope, and formation of microtubule complexes.
Ques 10: The following type of division results in the formation of gametes and sex cells having a haploid nature, unlike the diploid parent cell:
- Mitosis
- Meiosis
- Apogamy
- Miosis
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Ans: b. Meiosis
Explanation: Meiosis is a specialized kind of cell division that reduces the chromosome number by half and results in the production of haploid daughter cells. Meiosis forms 4 haploid daughter cells from one parent cell.
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