Which structure forms as DNA unwinds?
A replication fork forms as DNA unwinds.
The replication of DNA is semi-conservative, which means that it produces two copies in which each contains one of the original strands and one new strand. The enzyme helicase breaks the hydrogen bonds holding the two strands of DNA together, and DNA polymerase catalyzes the addition of new nucleotides to pair with the nucleotides in each original strand. The point at which the two strands of DNA separate is called the replication fork.