Structure of the orgin of DNA replication of bacteriophage fd

An RNA-polymerase-protected DNA fragment of 125 nucleotides from the origin of single-strand to double-strand replication of bacteriophage fd (ori-DNA) was located on the physical map of the phage genome. A stretch of 187 base pairs of DNA including the ori-DNA was sequenced. This DNA segment contains regions with a highly asymmetric pyrimidine/purine distribution next to regions with 2-fold symmetry that form stable hairpin structures in the viral DNA strand.