A system to unambiguously describe the configurations of molecules with more than one asymmetric center was devised in 1956 by Robert Cahn, Christopher Ingold, and Vladimir Prelog. In the Cahn–Ingold– Prelog or RS system

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#Id: 8656

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In budding yeast CKI p27 = Sic1 in metazoans

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When CDK activity is low= helicases are loaded in G1

When CDK activity is high= helicases are activated in

S, G2 & M

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Phosphorylation of MCM helicase activators by G1/S phase CDKs and S phase CDKs, prevents reloading of MCM helicases (ensuring that replication from each origin occurs only once during each cell cycle)

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Geminin 

a small protein,, that contributes to the inhibition of re-initiation at origins until cells complete a full cell cycle.