title: Molecular evolution of the Escherichia coli chromosome. II. Clonal segments.
abstract: Remarkable sequence similarities in the trp region among Escherichia coli strains of diverse natural origins imply the existence of worldwide clones of very recent origin. This in turn implies a low rate of fixation of new universally favorable alleles, which carry adjacent stretches of chromosome to high frequency. These clonal segments begin as entire chromosomes; recombination shortens them progressively by substituting less closely related homologous DNA. The rate of this recombination, comprising the introduction of a homologous chromosomal fragment to a cell and the replacement of part of the original chromosome, is estimated from observations.
authors.affiliation: Department of Biology, University of Iowa, Iowa City 52242.
authors.forename: R
authors.initials: R
authors.lastname: Milkman
authors.forename: A
authors.initials: A
authors.lastname: Stoltzfus
mesh_terms: D005075:Biological Evolution; D002876:Chromosomes, Bacterial; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics* / Q000648:ultrastructure; D009154:Mutation; D011110:Polymorphism, Genetic