Molecular evolution of the Escherichia coli chromosome. II. Clonal segments.

[摘要] 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.

[学科分类] 医学（综合）