pTZ19R/U was developed by inserting phage f1 intergenic region (IG) DNA into pUC19 and T7 close to the pUC19 MCS A small phagemid with a length of 2862 bp was constructed from the promoter sequence. The phagemids were oriented differently in the cloned f1 IG region. Designed to achieve DNA cloning, dideoxyDNA sequencing, in vitro mutation and in vitro transcription in one system. Host strains carrying these phagemids will produce single-stranded DNA if superinfected with helper phage M13K07.