Final answer:
The statement that a hairpin structure requires DNA to be single-stranded is True. Hairpins are formed when single-stranded DNA or RNA folds back on itself, allowing bases within the strand to pair up and form a stem-loop structure.
Step-by-step explanation:
For a hairpin to form, the DNA must be single-stranded. This statement is True.
Hairpin structures are formed when a single-stranded DNA folds back on itself and the bases within the same strand pair with each other, creating a stem-loop structure. This can occur during various biological processes, such as transcription termination, where the formation of a hairpin in the newly synthesized RNA transcript signals the end of the transcription.
DNA replication involves unwinding the double helix to create two single strands that then serve as templates for new strands. In this process, certain enzymes, like helicase, untwist the helix and single-strand binding proteins stabilize the unwound DNA.