Structurally, DNA is a flexible molecule. Even after completing almost seven decades, research in this field astonishes fast, and each new day emerges with gripping information. The first B-DNA structure proposed by Watson–Crick is proven as a milestone in the history of science and paved the way for exploring and understanding of all life processes. The voyage of studying DNA architecture is continued since after its discovery by James Watson and Francis Crick in 1953.

This would provide an insight to understand the biological functions of these unusual DNA structures and their recognition as potential therapeutic targets for diverse genetic diseases. The present review is a modest attempt to summarize the available literature, illustrating the occurrence of non-canonical structures at the molecular level in response to the environment and interaction with ligands and proteins. These non-B-DNA structures are expected to play a key role in determining genetic stability, DNA damage and repair etc. However, altered levels of gene expression are associated with many human genetic diseases including neurological disorders and cancer. In response to these various factors, the polymorphism of DNA regulates various genes via different processes like replication, transcription, translation, and recombination. The diversity in the DNA structure depends on various factors such as base sequence, ions, superhelical stress, and ligands. Apart from the predominant B-form, experimental shreds of evidence have revealed the existence of a sequence-dependent structural diversity, unusual non-canonical structures like hairpin, cruciform, Z-DNA, multistranded structures such as DNA triplex, G-quadruplex, i-motif forms, etc. For the last seven decades, this has been a leading light in the course of the development of modern biology and biomedical science. 3Department of Chemistry, Rajdhani College, University of Delhi, New Delhi, IndiaĪ complete understanding of DNA double-helical structure discovered by James Watson and Francis Crick in 1953, unveil the importance and significance of DNA.2Department of Chemistry, Hansraj College, University of Delhi, Delhi, India.

1Nucleic Acid Research Lab, Department of Chemistry, University of Delhi, Delhi, India.

Aparna Bansal 1,2, Shikha Kaushik 1,3 and Shrikant Kukreti 1*

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