All Free Biology MCQs with Answers
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19844 questions · page 582 of 1985
5811. Concerning cell division and cell cycle, which statement is incorrect?
- A. After completion of interphase, mitosis is a dynamic and vigorous process
- B. Cytokinesis is usually followed by karyokinesis
- C. S sub-stage is followed by G-1
- D. Both B and C
Explanation: B is wrong: cytokinesis follows karyokinesis. C is wrong: sequence is G-1--->S---> G-2---> M
Correct answer: Cytokinesis is usually followed by karyokinesis5812. Cell-division without the formation of spindle is called:
- A. Amitosis
- B. Mitosis
- C. Meiosis
- D. Interphase
Explanation: Amitosis is direct cell division without spindle formation or chromosome condensation.
Correct answer: Amitosis5813. During cell growth, DNA synthesis takes place in the_ phase.
- A. S-phase
- B. G-1 phase
- C. G-2 phase
- D. M-phase
Explanation: In S-phase, DNA replicates, doubling the genetic material for division.
Correct answer: S-phase5814. When a cell has a stalled DNA replication fork, which checkpoint should be predominantly activated?
- A. G-1/S
- B. G-2/M
- C. M
- D. Both G-2/M and M
Explanation: The G-2/M checkpoint ensures DNA repication is complete before mitosis; a stalled fork triggers this checkpoint.
Correct answer: G-2/M5815. Spindle fibers attach onto the _ of the chromosome:
- A. Centromere
- B. Kinetosome
- C. Telomere
- D. Kinetochores
Explanation: Kinetochore is a protein complex on centromere where spindle fibers attach for chromosome movement.
Correct answer: Kinetochores5816. Which of the following is not a characteristic feature during mitosis in somatic cells?
- A. Chromosome movement
- B. Synapsis
- C. Spindle fibres
- D. Disappearance of nucleolus
Explanation: Synapsis occurs only in meiosis where homologous chromosomes pair. In mitosis, chromosomes do not pair, so synapsis is not a characteristic.
Correct answer: Synapsis5817. In meiosis, crossing over is initiated at the:
- A. Zygotene
- B. Diplotene
- C. Pachytene
- D. Leptotene
Explanation: Pachytene is when non-sister chromatids exchange. segments at chiasmata.
Correct answer: Pachytene5818. A somatic cell that has just completed the S phase, compared to a gamete, has:
- A. Twice the chromosomes & four times the DNA
- B. Four times the chromosomes & twice the DNA
- C. Twice the chromosomes & same DNA
- D. Same chromosomes & twice the DNA
Explanation: After S-phase, diploid somatic cell has replicated DNA: 2x chromosomes and 4x DNA content compared to gametes.
Correct answer: Twice the chromosomes & four times the DNA5819. The grey crescent area in an embryo is present:
- A. Just below sperm entry
- B. Just above sperm entry
- C. Just opposite sperm entry
- D. Just adjacent to sperm entry
Explanation: Marks future dorsal side; forms opposite sperm entry.
Correct answer: Just opposite sperm entry5820. Centromere region where spindle fibres attach is:
- A. Centromere
- B. Kinetochore
- C. Telomere
- D. Kinetosome
Explanation: Kinetochore is the attachment point for spindle fibers.
Correct answer: Kinetochore