  We show that a null-homologous transverse knot K in the complement of an
overtwisted disk in a contact 3-manifold is the boundary of a Legendrian ribbon
if and only if it possesses a Seifert surface S such that the self-linking
number of K with respect to S satisfies $\sel(K,S)=-\chi(S)$. In particular,
every null-homologous topological knot type in an overtwisted contact manifold
can be represented by the boundary of a Legendrian ribbon. Finally, we show
that a contact structure is tight if and only if every Legendrian ribbon
minimizes genus in its relative homology class.
