Physics of DNA: unravelling hidden abilities encoded in the structure of 'the most important molecule'

A comprehensive article Structure and Interactions of Biological Helices'', published in 2007 in Reviews of Modern Physics, overviewed various aspects of the effect of DNA structure on DNA-DNA interactions in solution and related phenomena, with a thorough analysis of the theory of these effects. Here, an updated qualitative account of this area is presented without any sophisticated 'algebra'. It overviews the basic principles of the structure-specific interactions between double-stranded DNA and focuses on the physics behind several related properties encoded in the structure of DNA. Among them are ( i) DNA condensation and aptitude to pack into small compartments of cells or viral capcids, ( ii) the structure of DNA mesophases, and (iii) the ability of homologous genes to recognize each other prior to recombination from a distance. Highlighted are some of latest developments of the theory, including the shape of the 'recognition well'. The article ends with a brief discussion of the first experimental evidence of the protein-free homology recognition in a 'test tube'.