Genetische Untersuchungen am Bakteriophagen ?X 174

Pfeifer, Dietrich

doi:10.1007/bf00890055

Cited by 5 publications

(3 citation statements)

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“…We suggest that figure 8 structures are responsible for most of the 2- (Table 1) (2) Figure 8 structures that are recombinant are generated by "single-strand aggression" and are stabilized by "branch migration." "Single-strand aggression" is a process catalyzed by the host recA + protein in which an RF DNA molecule containing a single strand region interacts with another RF DNA molecule, ultimately leading to a recombination event (11).…”

Section: Resultsmentioning

confidence: 96%

“…Such DNA structures were observed to be formed preferentially in host recA+ cells or recA + cell-free systems. Since the host recA + allele is required for most 4OX174 recombinant formation, we conclude that the observed figure 8 molecules are intermediates in, or end products of, a 4X174 recombination event.We propose that recombinant figure 8 DNA molecules arise as a result of "single-strand aggression," are stabilized by double-strand "branch migration," and represent a specific example of a common intermediate in genetic recombination.Genetic recombination in bacteriophage OX174 (1,2) and in the closely related bacteriophage S13 (3) has been analyzed extensively by both genetic (4-9) and physical (10-16) methods. Most OX174 recombinants are formed by a major pathway, Tessman's primary mechanism (4, 5), which requires the host recA + allele (6) but apparently does not need any of the nine known OX174 gene products (7).…”

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confidence: 99%

“…Genetic recombination in bacteriophage OX174 (1,2) and in the closely related bacteriophage S13 (3) has been analyzed extensively by both genetic (4-9) and physical (10)(11)(12)(13)(14)(15)(16) methods. Most OX174 recombinants are formed by a major pathway, Tessman's primary mechanism (4,5), which requires the host recA + allele (6) but apparently does not need any of the nine known OX174 gene products (7).…”

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confidence: 99%

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Recombinant DNA molecules of bacteriophage phi chi174.

Benbow¹,

Zuccarelli²,

Sinsheimer³

1975

Proc. Natl. Acad. Sci. U.S.A.

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ABSTRACT4 X174 DNA structures containing two different parental genomes were detected genetically and examined by electron microscopy. These structures consisted of two monomeric double-stranded DNA molecules linked in a figure 8 configuration. Such DNA structures were observed to be formed preferentially in host recA+ cells or recA + cell-free systems. Since the host recA + allele is required for most 4OX174 recombinant formation, we conclude that the observed figure 8 molecules are intermediates in, or end products of, a 4X174 recombination event.We propose that recombinant figure 8 DNA molecules arise as a result of "single-strand aggression," are stabilized by double-strand "branch migration," and represent a specific example of a common intermediate in genetic recombination.Genetic recombination in bacteriophage OX174 (1,2) and in the closely related bacteriophage S13 (3) has been analyzed extensively by both genetic (4-9) and physical (10-16) methods. Most OX174 recombinants are formed by a major pathway, Tessman's primary mechanism (4, 5), which requires the host recA + allele (6) but apparently does not need any of the nine known OX174 gene products (7). Recombinant formation via this major pathway involves two parental replicative form (RF) DNA molecules (5, 7), and occurs very early in the infection process (10). Single recombination events via the major pathway usually generate only one parental genotype and one recombinant (7). The goal of this work was to identify OX174 DNA structures which were formed by this major pathway.To determine whether a particular DNA structure was recombinant, parental replicative form DNA molecules were isolated from cells infected with two parental genotypes (11). After purification and fractionation of the DNA molecules by velocity and equilibrium sedimentation procedures (12, 13), the frequency of recombinants associated with various DNA structures was examined genetically using a spheroplast assay in which further recombination could not occur (10). In addition, we were able to identify putative recombinant DNA molecules formed in mixed infections by using two parental genotypes which could be distinguished by electron microscopy (13).In this paper we present electron micrographs of OX174 DNA molecules which apparently are recombinant. These structures appear to be "figure 8" molecules (15,17) We propose a simple mechanism to generate figure 8 DNA molecules that are recombinant. It is based on two molecular processes-"single-strand aggression" (11) and "branch migration" (19-21). These were previously implicated in recombinant formation in OX174 (10,11,13,15) and in other organisms (20,22). MATERIALS AND METHODSReplicative form and multiple length DNA molecules were isolated from cells infected with two genotypes (9, 11, 13, 23; R. M. Benbow, M. Eisenberg, and R. L. Sinsheimer, to be published). The fractionated DNA molecules were examined for recombinants by carrying out spheroplast infections (24), after which the progeny phage were assayed for wild-type recombina...

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Section: Resultsmentioning

confidence: 96%

mentioning

confidence: 99%