DNA is an iconic molecule that forms a double helical structure, providing the basis for genetic inheritance, and its physical properties have been studied for decades. In this talk, I will present evidence that sequence and methylation dependent physical properties of DNA such as flexibility and self-association may be important for biological functions [1, 2]. In addition, I will present a new application of DNA where mechanical modulations of cell behavior can be studied at the single molecule level using rupturable DNA tethers . We found that cells can change their behavior dramatically in response to just two molecules strongly tugging on them .
 R. Vafabakhsh and T. Ha, “Extreme bendability of DNA less than 100 base pairs long revealed by single molecule cyclization”, Science 337, 1097-1101 (2012).
 T. Ngo, Q. Zhang, R. Zhou, J. G. Yodh and T. Ha, “Asymmetric unwrapping of nucleosomes under tension directed by DNA local flexibility”, Cell 160, 1135-1144 (2015).
 X. Wang and T. Ha, “Defining Single Molecular Forces Required to Activate Integrin and Notch Signaling”, Science 340, 991-994 (2013).
 M. Roein-Peikar, Q. Xu, X. Wang and T. Ha, “Ultrasensitivity of cell adhesion to the presence of mechanically strong ligands,” Physical Review X (2016).