DNA replication occurs during interphase
Before a cell divides, it must copy all of its DNA. This copying happens during interphase — the preparation stage of the cell cycle.
Formula
S phase: 1 DNA molecule → 2 identical DNA molecules (semi-conservative replication)
Real World
Cancer chemotherapy drugs such as methotrexate work by blocking enzymes needed during S phase, halting DNA replication so rapidly dividing tumour cells cannot copy their DNA and divide.
Exam Focus
Specify that replication occurs in the S (synthesis) sub-stage of interphase, not interphase generally, for full marks.
Evaluation Scaffold
A four-step framework for high-quality evaluation. Use this for 'assess', 'evaluate', and 'to what extent' questions.
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