Q.Can there be mitosis without DNA replication in 'S' phase?
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Start your 14-day free trial to unlock the full solution →No — mitosis depends on the DNA replication of the S phase, because without duplicated chromosomes there are no sister chromatids to separate, and the two daughter cells could not each receive a complete, identical genome.
To answer this we need to remember what mitosis is for and how the cell cycle is arranged. Mitosis is an equational division: its whole point is to give each of the two daughter cells exactly the same, complete set of chromosomes as the parent. For that to be possible, the genetic material must be duplicated before division begins.
Why replication has to come first
- DNA synthesis is confined to one particular stage of the cell cycle — the S phase of interphase — and does not go on throughout the cycle.
- During S phase the amount of DNA per cell doubles, so that each chromosome comes to consist of two identical sister chromatids joined at the centromere.
- Mitosis then separates these sister chromatids, one to each pole, so that both daughter cells end up with a full set of chromosomes identical to the parent's.
What would happen without S phase
- If the S phase were skipped, the chromosomes would never be duplicated.
- With no duplication there would be no pairs of sister chromatids for anaphase to pull apart. …
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