DNA arms do the legwork to ensure the directionality of lambda site-specific recombination.

Radman-Livaja M., Biswas T., Ellenberger T., Landy A., & Aihara, H. (2006). “DNA arms do the legwork to ensure the directionality of lambda site-specific recombination.” Curr Opin Struct Biol. 2006 Feb;16(1):42-50. Epub 2005 Dec 20. (Abstract)