Why is DNA uncoiled from the protein before replication?
To expose the parts that need replicating.
As you may know, our DNA is coiled on histone proteins, proteins that keep our DNA from tangling.
The thing is though, that if the DNA is wrapped tightly around these proteins, it is super hard to access it in order to start replication. Hence, we need to get it away from the protein (untwine) so that we can access it to start replication.