Here's a breakdown:

* Helicase is a crucial enzyme in both DNA replication and RNA transcription. Its primary function is to break the hydrogen bonds between the nitrogenous bases in DNA and RNA, unwinding the double helix and separating the two strands.

* In DNA replication, helicase unwinds the DNA molecule, allowing each strand to serve as a template for the synthesis of a new complementary strand.

* In RNA transcription, helicase unwinds a portion of the DNA molecule, exposing the template strand for RNA polymerase to transcribe into a messenger RNA (mRNA) molecule.

Therefore, helicase is the key enzyme responsible for unzipping both DNA and RNA, enabling crucial biological processes like DNA replication and transcription.