Answer:
<em><u>The water in lakes comes from rain, snow, melting ice, streams, and groundwater seepage. If water leaves a lake by a river or other outlet, it is said to be open. All freshwater lakes are open. If water only leaves a lake by evaporation, the lake is closed.</u></em>
DNA is unzipped by helicase at the origin of replication. There are several origins of replications in eukaryotic DNA replication, while only one in prokaryotic replication.