A 300 bp long B- form of plasmid DNA has 20 complete turns. This DNA molecule is:
The principle of nucleic acid structure and recombination explains that hairpin formation, Holliday junction resolution and translation control ensure fidelity. Hence Negatively supercoiled fits best because it matches molecular mechanisms, as documented in authoritative sources on molecular biology.
Ref: Watson et al., Molecular Biology of the Gene, 7th Edition, Chapter 9, Transcription and RNA Processing, describes RNA hairpin formation, secondary structures and regulatory mechanisms controlling gene expression.
