CELL STRUCTURES AND FUNCTION
CELL CYCLE
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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G1 phase
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S phase
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G2 phase
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None of the above
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Detailed explanation-1: -S phase is the period during which DNA replication occurs.
Detailed explanation-2: -DNA replicates in the S phase of the cell cycle and initiates at specific regions in the DNA sequence known as DNA replication ‘origins’. A number of proteins participate in DNA replication and the process is subject to scrutiny by cell surveillance mechanisms called cell cycle checkpoints.
Detailed explanation-3: -During the S phase, DNA is duplicated into two sister chromatids, and centrosomes, which give rise to the mitotic spindle, are also replicated. In the G2 phase, energy is replenished, new proteins are synthesized, the cytoskeleton is dismantled, and additional growth occurs.
Detailed explanation-4: -Initially in G1 phase, the cell grows physically and increases the volume of both protein and organelles. In S phase, the cell copies its DNA to produce two sister chromatids and replicates its nucleosomes. Finally, G2 phase involves further cell growth and organisation of cellular contents.
Detailed explanation-5: -The G2 phase follows the S-phase. In this phase, the cell prepares for mitotic division. Before DNA replication, the chromosome number remains the same. After the S-phase, the DNA replicates, and the number of chromosomes doubles.