**4. Biological significance of DNA abnormal folding**

Apart from the roles in DNA replication, transcription and gene regulation, non-B DNA may also lead to gene instability, including chromosomal translocation, deletion and amplification in cancer and other human diseases ( Bacolla & Wells, 2009; Chen et al., 2010). Since non-B DNA abnormal folds have been addressed with generating DNA breaks, including both single and double strand DNA breaks. Non-B DNA structures recruit DNA repair machinery to the breaking sites, which then make gene mutations and chromosomal rearrangements during repair.
