The term "unzipping" in the DNA replication refers to the breaking of the hydrogen bonds.
In the process of DNA replication, DNA helicases
disentangle DNA at positions known as origins where synthesis will be
initiated. DNA helicases continue to uncoil the DNA creating a structure called replication fork
as they unzipped apart. The process of breaking the hydrogen bonds between the
nucleotide base pairs in double-stranded DNA needs energy. Helicases require
energy stored in an ATP molecule to break the bonds.
