Universal bases for hybridization, replication and chain termination

Several unnatural, predominantly hydrophobic nucleobases that pack efficien tly in duplex DNA without hydrogen bonding functionalities are reported to circumvent the hydrogen bonding-based specificity, both during oligonucleot ide hybridization and enzymatic DNA synthesis. The reported nucleoside anal ogs are efficient 'universal bases' for hybridization, template directed DN A synthesis and chain termination. Moreover, several of the universal bases function in their biological role, hybridization or replication, with an e fficiency not significantly reduced relative to their natural counterparts.