[Homologous recombination between direct repeats of chromosomal segments comprising heterozygotic duplications in Escherichia coli].
In conjugational matings between double mutants for the deo operon of Escherichia coli, haploid recombinants and extended tandem duplications deoC deoD/deoA deoB::Tn5 with the DeoC+DeoA+DeoB+DeoD- phenotype are formed (the deoD+ allele is not expressed due to the polar effect of the Tn5 insertion). Selection for the expression of the recessive deoC deoD alleles (in the thyA genome) leads to the segregation of haploid clones by duplications and also of clones that retain the diploidy but that are homozygous for deoC deoD. In addition to haploids, diploid clones retaining the duplications have also been found among the DeoD+ segregants. The phenotype of segregants retaining the duplication shows that they were formed by an unequal exchange between sister chromosomes. A comparison of segregation frequency of haploid and diploid DeoD+ clones in rec+ and recBC sbcB sbcC strains shows that duplications in the rec+ genome are more stable. On this basis, it is assumed that the RecBCD pathway possibly makes a greater contribution than the RecF pathway to the preservation of heterozygous duplications playing an important role in the evolution of prokaryotes.
State Research Institute of Genetics and Selection of Industrial Microorganisms, Moscow, Russia. lab2@genetika.ru
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Sukhodolets
D002876:Chromosomes, Bacterial / Q000235:genetics*; D004171:Diploidy; D004926:Escherichia coli / Q000235:genetics*; D020440:Gene Duplication; D006238:Haploidy; D006579:Heterozygote; D011995:Recombination, Genetic