Identification of Recombinant Chromosomes and F-Merogenotes in Merodiploids of Escherichia coli

Segregants from merodiploids heterozygous at two or more sites in the lac region were selected on the basis of containing a recombinant F-merogenote. Such recombinants frequently contained a recombinant chromosome as well. When the merodiploid was heterozygous at two sites, the frequency at which reciprocally recombinant chromosomes were present in the selected population was lower when the two marked sites were in the same gene and close together than when the sites were more widely separated. When the merodiploid was heterozygous at four sites and selection was made for an intragenic recombinational event, the recombinant chromosome was the reciprocal type about half the time and about half the time was not. Among the latter genotypes, most were nonrecombinant for the intragenic pair of markers. The data are consistent with a model in which recombination leads to the formation of two recombinant products, each containing a region of hybrid deoxyribonucleic acid.