Which best describes the mechanismwhereby a cell allows DNA to be replicated onl
ID: 4979 • Letter: W
Question
Which best describes the mechanismwhereby a cell allows DNA to be replicated only once per cell cycle?A. The cell monitors the concentration ofnucleotides available for DNA synthesis. B. The cellallows DNA to be replicated only if it lacks damage. C. The cellcontrols separation of DNA to daughter cells only duringmitosis. D. The cellmakes a labile protein required to initiate DNA replication onlyonce per cell cycle. E. The cell uses a DNA damage check-pointto ensure replication only once per cycle. Which best describes the mechanismwhereby a cell allows DNA to be replicated only once per cell cycle?
A. The cell monitors the concentration ofnucleotides available for DNA synthesis. B. The cellallows DNA to be replicated only if it lacks damage. B. The cellallows DNA to be replicated only if it lacks damage. C. The cellcontrols separation of DNA to daughter cells only duringmitosis. C. The cellcontrols separation of DNA to daughter cells only duringmitosis. D. The cellmakes a labile protein required to initiate DNA replication onlyonce per cell cycle. D. The cellmakes a labile protein required to initiate DNA replication onlyonce per cell cycle.
Explanation / Answer
E. The cell uses a DNA damagecheck-point to ensure replication only once percycle. An important aspect of cellbehaviour is that DNA replication happens only once per cell cycle.Replicated DNA is unable to re-replicate until cell division hasoccurred. Unreplicated DNA is in a replication-competent or'licensed' state. The ability to replicate is lost in S phase andregained following passage through mitosis. Recent evidence hasimplicated an MCM (minichromosome maintenance) protein complex andthe Cdc6 protein in determining replication competence.Regeneration of replication competence upon passage through mitosisentails changes in protein kinase activity, of which the MCMs are alikely target. Features of the mechanism that restricts DNAreplication to once per cell cycle appear to be conservedthroughout eukaryotes.
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