DNA is unzipped during its replication process; the two strands of the double helix are separated and a new complementary DNA strand is synthesized from the parent strands. Also, during DNA transcription, one DNA strand, known as the template strand, is transcribed (copied) into an RNA strand. In order for the two strands of DNA to separate, the hydrogen bonds between the nitrogen bases must be broken. DNA helicase breaks the bonds. However, the enzyme does not actually unwind the DNA; there are special proteins that first separate the DNA strands at a specific site on the chromosome. These are called initiator proteins.