As demonstrated by means of DNA nanoconstructs(1), as well as DNA functionalization of nanoparticles(2-4) and micrometre-scale colloids(5-8), complex self-assembly processes require components to associate with particular partners in a programmable fashion. In many cases the reversibility of the interactions between complementary DNA sequences is an advantage(9). However, permanently bonding some or all of the complementary pairs may allow for flexibility in design and construction(10). Here, we show that the substitution of a cinnamate group for a pair of complementary bases provides an efficient, addressable, ultraviolet light-based method to bond complementary DNA covalently. To show the potential of this approach, we wrote micrometre-scale patterns on a surface using ultraviolet light and demonstrated the reversible attachment of conjugated DNA and DNA-coated colloids. Our strategy enables both functional DNA photolithography and multistep, specific binding in self-assembly processes.