Abstract
A DNA-DNA hybridization technique using isolated F'DNA was examined for its qualification as a method of determining amounts of several specific regions of bacterial chromosome, and applied to a study on the origin and direction of chromosomal replication in Escherichia coli K 12. Marker frequency analysis gave an evidence against the fixed origin-unidirectional replication model. Three possible models are proposed for the origin and direction of chromosomal replication of E. coli.
