Concerning pyrimidine dimers as "blocks" to DNA replication in bacteria and mammalian cells.

Irradiated UV-sensitive bacteria which are mutant in the uvrA6 locus, and cannot excise pyrimidine dimers, are capable of continued DNA replication with the same orientation as that in unirradiated cells. Replication of dimer-containing DNA is also accomplished by irradiated mammalian cells, suggesting that pyrimidine dimers do not act as absolute blocks to DNA synthesis. Thus, the role that dimers play in reducing the amount and size of DNA synthesized after exposure must be reassessed.