Cell cycle, mitosis, meiosis
- What is the main function of the spindle fibers during mitosis ? Answer: 1. To separate the chromosomes Key idea: Spindle fibres are microtubules that attach to the kinetochores. During anaphase they pull... 1
- Following are the stages of cell division :A. Gap 2 phaseB. CytokinesisC. Synthesis phaseD. KaryokinesisE. Gap 1 phaseChoose the correct sequence of stages from the options given below : Answer: 1. E-C-A-D-B Key idea: interphase comes first (G1, S, G2), then M phase (karyokinesis, then cytokinesis). G1 (E) → S (C) → G2 (A) →... 1
- Match List I with List II :List I (Sub Phases of Prophase I):A. DiakinesisB. PachyteneC. ZygoteneD. LeptoteneList II (Specific characters):I. Synaptonemal complex formationII. Completion of terminalisation of chiasmataIII. Chromosomes look like thin… Answer: 4. A-II, B-IV, C-I, D-III Key idea: order of prophase I: leptotene, zygotene, pachytene, diplotene, diakinesis. Diakinesis - termina... 1
- Spindle fibers attach to kinetochores of chromosomes during Answer: 3. Metaphase Key idea: chromosomes line up at the equator in metaphase, with spindle fibres attached to their kinetochores. In metap... 1
- Given below are two statements:Statement I : Chromosomes become gradually visible under light microscope during leptotene stage.Statement II : The begining of diplotene stage is recognized by dissolution of synaptonemal complex.In the light of the ab… Answer: 2. Both Statement I and Statement II are true Key idea: recall what happens in each substage of prophase I. Statement I: In leptoten... 1
- Given below are two statements:Statement I: During G_0 phase of cell cycle, the cell is metabolically inactive.Statement II: The centrosome undergoes duplication during S phase of interphase.In the light of the above statements, choose the most appro… Answer: 1. Statement I is incorrect but Statement II is correct. Key idea: G₀ is a quiescent stage, not a dead stage. Statement I is incorre... 1
- Select the correct statements.A. Tetrad formation is seen during Leptotene.B. During Anaphase, the centromeres split and chromatids separate.C. Terminalization takes place during Pachytene.D. Nucleolus, Golgi complex and ER are reformed during Teloph… Answer: 3. B and D only Key idea: Check the stages of cell division. A is wrong: tetrads form in pachytene, after synapsis; leptotene is the... 1
- The process of appearance of recombination nodules occurs at which sub stage of prophase I in meiosis? Answer: 3. Pachytene Key idea: Recombination nodules appear during pachytene, when crossing over takes place between non-sister chromatids o... 1
- Among eukaryotes, replication of DNA takes place in - Answer: 3. S phase Key idea: DNA replication in eukaryotes takes place in the S (synthesis) phase of interphase. G1 is for cell growth, G2 f... 1
- Match List I with List II :List I | List IIA. M Phase | I. Proteins are synthesizedB. G_2 Phase | II. Inactive phaseC. Quiescent stage | III. Interval between mitosis and initiation of DNA replicationD. G_1 Phase | IV. Equational divisionChoose the c… Answer: 4. A-IV, B-I, C-II, D-III Key idea: Match each phase with its feature. M phase: equational division (IV). G2 phase: proteins are syn... 1
- Select the incorrect statement with reference to mitosis : Answer: 3. Spindle fibres attach to centromere of chromosomes. Key idea: Spindle fibres attach to the kinetochores, which are protein discs... 1
- Regarding Meiosis, which of the statements is incorrect ? Answer: 3. DNA replication occurs in S phase of Meiosis-II Key idea: DNA replicates only once in meiosis, in the S phase before meiosis I. M... 1
- Which one of the following never occurs during mitotic cell division ? Answer: 4. Pairing of homologous chromosomes Pairing of homologous chromosomes (synapsis) is a feature of meiosis I, never of mitosis. In mi... 1
- The appearance of recombination nodules on homologous chromosomes during meiosis characterizes : Answer: 4. Sites at which crossing over occurs Recombination nodules are protein-rich structures seen in the pachytene stage on the synapton... 1
- The fruit fly has 8 chromosomes (2n) in each cell. During interphase of Mitosis if the number of chromosomes at G_1 phase is 8, what would be the number of chromosomes after S phase ? Answer: 1. 8 The chromosome number does not change in S phase; only DNA content doubles, because each chromosome gets two sister chromatids... 1
- Which stage of meiotic prophase shows terminalisation of chiasmata as its distinctive feature ? Answer: 3. Diakinesis Terminalisation of chiasmata (chiasmata slide towards the ends of the bivalents) occurs in diakinesis, the last stage... 1
- The centriole undergoes duplication during : Answer: 1. S-phase Centrioles duplicate during the S phase of the cell cycle (in the cytoplasm, alongside DNA replication), so that two cent... 1
- Match List - I with List - II.List - I | List - II(a) S phase | (i) Proteins are synthesized(b) G2 phase | (ii) Inactive phase(c) Quiescent stage | (iii) Interval between mitosis and initiation of DNA replication(d) G1 phase | (iv) DNA replicationCho… Answer: 3. (a)-(iv), (b)-(i), (c)-(ii), (d)-(iii) Match each phase: S phase: DNA replication, (a)-(iv). G2 phase: proteins are synthesised f... 1
- Which of the following stages of meiosis involves division of centromere ? Answer: 3. Anaphase II In meiosis, sister chromatids separate only in anaphase II, when the centromere splits and each chromatid becomes a s... 1
- Dissolution of the synaptonemal complex occurs during : Answer: 3. Diplotene The synaptonemal complex forms in zygotene, is complete in pachytene and dissolves in diplotene, when homologues separa... 1
- Match the following with respect to meiosis :(a) Zygotene (i) Terminalization(b) Pachytene (ii) Chiasmata(c) Diplotene (iii) Crossing over(d) Diakinesis (iv) SynapsisSelect the correct option from the following : Answer: 2. (a) (iv), (b) (iii), (c) (ii), (d) (i) Link each meiotic prophase I sub-stage to its main event. Zygotene: pairing of homologous... 1
- Some dividing cells exit the cell cycle and enter vegetative inactive stage. This is called quiescent stage (G_0). This process occurs at the end of : Answer: 2. G ₁ phase Cells leave the cell cycle to enter the G0 (quiescent) stage at the end of G1 phase, before the S phase begins. They re... 1
- Identify the correct statement with regard to G_1 phase (Gap 1) of interphase. Answer: 3. Cell is metabolically active, grows but does not replicate its DNA. Key idea: G₁ is the growth phase before DNA replication. In G... 1
- Cells in G_0 phase : Answer: 3. suspend the cell cycle Cells that do not divide further leave the active cycle at G₁ and enter the quiescent G₀ stage. They remai... 1