The level of protein structure that will remain intact is the primary structure of proteins that corresponds to the number of amino acids and the peptide bonds. The secondary structures (alpha helices or beta sheets), the tertiary structures (whether globular or fibrous), and the quaternary structures (multiple subunits) will all be denatured.
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.
