How can meters of genetic material be packed in mammalian sperm and phage heads? Why do some ions condense DNA, while others do not? Why does DNA change its structure in dense aggregates? These and other questions, including a mechanism for snap-shot genegene recognition in recombination of homologous genes suggested by Kornyshev and Leikin are addressed within an ongoing research program of a ‘transatlantic’ team at the Departments of Chemistry and Molecular Biosciences of Imperial College London, and the Physical Biochemistry Group of the Institute of Child Health and Human Development of the National Institute of Health (Bethesda, MD, USA). This project is based on Kornyshev-Leikin theory of interaction of helical macromolecules in solutions. In line with a wealth of experimental data (such as the observed poly- and meso-morphism of DNA assemblies, and the measured decay range of repulsive forces between various helical macromolecules) this theory was recently extended to the statistical mechanics of DNA columnar and cholesteric phases, and DNA mechanics - mapped on forefront models of nonlinear physics (A. Cherstvy, A. Kornyshev, D.J. Lee, S. Leikin, A. Wynveen). One of the recent results was the experimental proof of azimuthal correlations between DNA in hydrated aggregates (A.A. Kornyshev, D.J. Lee, S. Leikin, A. Wynveen, S. Zimmerman), predicted by the theory. The latest experiments of Imperial-NIH team (G. Baldwin, N. Brooks, A. Goldar, S. Leikin, R. Robson, J. Seddon) has recently approved existence of the physical mechanism of homology recognition in protein free environment, predicted by KL in 2001. The effect of homology recognition is what presumably warrants against errors in homologous recombination of genes – the process responsible for evolution and genetic diversity, as well DNA repair. Thus understanding the recognition mechanism may result in the future in understanding how to avoid such errors that themselves are responsible for a number of genetically determined diseases, such as cancer and Atzheimer’s on one hand, or aging on the other hand. This talk will introduce the audience to the principles of the theory, present some of its main results, and review the latest experimental findings. An interested listener is referred to a detailed article which will be published in the June issue of Reviews of Modern Physics: A.A. Kornyshev, D.J. Lee, S. Leikin, and A. Wynveen: Structure and interactions of biological helices, and the original publications, listed below. Theory of interaction between helical molecules A.A.Kornyshev and S.Leikin, J.Chem.Phys. 1997,107, 3656. Symmetry laws for interaction between helical macromolecules. A.A.Kornyshev and S.Leikin, Biophys.J., 1998, 75, 2513. Helical symmetry and electrostatic interaction of macromolecules in dense aggregates. An impetus for DNA poly- and meso-morphism. A.A.Kornyshev and S.Leikin, Proc.Natl.Acad.Sci.USA. 1998, 95, 13579. Electrostatic zipper motif for DNA aggregation. A.A.Kornyshev and S.Leikin, Phys.Rev.Lett., 1999, 82, 4138. A twist in chiral interaction between biological helices. A.A.Kornyshev and S.Leikin, Phys.Rev.Lett. 2000, 84, 2537. Electrostatic interaction between long, rigid helical macromolecules at all interaxial angles A.A.Kornyshev and S.Leikin, Phys.Rev.E, 2000, 62, 2576. Sequence recognition in pairing of DNA duplexes. A.A.Kornyshev and S.Leikin, Phys.Rev.Lett. 2001, 86, 3666. DNA need not unzip.- http://focus.aps.org/v7/st19.html Chiral electrostatic interactions and cholesteric liquid crystals of DNA. A.A.Kornyshev, S.Leikin, and S.Malinin, European Phys.J. E (Soft Matter) 2002, 7, 83. Phase behavior of columnar DNA assemblies. H.M.Harreis, A.A.Kornyshev, C.N.Likos, H.Loewen, and G.Sutmann, Phys.Rev.Lett. 2002, 89, art.#18303. Temperature-dependent DNA condensation triggered by rearrangement of adsorbed cations. A.G. Cherstvy, A.A.Kornyshev, S.Leikin, J.Phys.Chem.2002,106, 13362. Torsional Deformation of Double Helix in Interaction and aggregation of DNA. A.G.Cherstvy, A.A.Kornyshev, and S.Leikin, J.Phys.Chem.B, 2004, 108, 6508. Nonlinear effects in torsional adjustment of interacting DNA. A.Kornyshev and A.Wynveen,. Phys.Rev.E, 2004, 69, #041905, 1-14. DNA-DNA interaction beyond the ground state. D.J.Lee, A.Wynveen, and A.A.Kornyshev, Phys. Rev. E, 2004, 70, #051913, 1-12 Statistical mechanics of DNA assemblies. A.Wynveen, D.J.Lee, and A.A.Kornyshev, Eur.Phys.J. E, 2005, 16, 303. Torsional fluctuations in columnar DNA assemblies. D.J.Lee and A.Wynveen, J.Phys: Condensed Matter, 18, 786 (2006). DNA melting in aggregates: impeded or facilitated? A.G.Cherstvy and A.A.Kornyshev, J.Phys.Chem.B, 2004, 108, 6508. Direct observation of azimuthal correlations between DNA in hydrated aggregates A.A.Kornyshev, D.J.Lee, S.Leikin, A.Wynveen, S.Zimmerman, Phys.Rev.Lett. 2005, 95,#148102.