Abstract
The replication of bacteriophage X-174 is impaired at temperatures above 40 °C. Mutants (ht) that replicate at high temperature were isolated and partially characterized. Wild-type X fails to grow at high temperature because, unlike the mutants, it does not make appreciable amounts of single-stranded (ss)DNA. An unusual form of ssDNA, not found in complete virions, is described.
* Present address: Institute of Molecular Biology, State University of Utrecht, Padualaan 8, 3508 TB Utrecht, The Netherlands.