SSC
BIOLOGY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Before mitosis begins, which happens before the nucleus starts dividing?
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The cytoplasm separates.
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The DNA replicates.
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The sister chromatids separate.
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The homolgous chromosomes cross over.
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Explanation:
Detailed explanation-1: -Before the cell undergoes mitosis, the cell must make two copies of its DNA so that each daughter cell has a complete copy of the genetic material. At the onset of mitosis the nuclear envelope dissolves, and each chromosome lines up with its copy.
Detailed explanation-2: -S phase is the period during which DNA replication occurs.
Detailed explanation-3: -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.
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