A temperature-sensitive recombination-deficient mutant, rec-126, has been isolated that permits high frequencies of recombination at the permissive temperature (25 degrees) but greatly decreases recombination at the restrictive temperature (31 degrees). The sensitive period for response of female germ cells carrying this mutant to the restrictive temperature has been defined. Sensitivity begins very close to the time the oocyte enters premeiotic interphase and initiates DNA synthesis; it continues for the duration of premeiotic-S; and it terminates with the completion of S. This time span precisely coincides with the sensitive period for enhancement of recombination by heat in the normal genome and is further characterized by the presence of the synaptonemal complex. These results provide compelling evidence for identifying premeiotic-S as the time of meiotic recombination.
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http://dx.doi.org/10.1073/pnas.75.7.3351 | DOI Listing |
Nucleic Acids Res
March 1997
Department of Biochemistry, Faculty of Medicine, Sir Charles Tupper Medical Building, Dalhousie University, Halifax, Nova Scotia B3H 4H7, Canada.
The cloning and propagation of large fragments of DNA on yeast artificial chromosomes (YACs) has become a routine and valuable technique in genome analysis. Unfortunately, many YAC clones have been found to undergo rearrangements or deletions during the cloning process. The frequency of transformation-associated alterations and mitotic instability can be reduced in a homologous recombination-deficient yeast host strain such as a rad52 mutant.
View Article and Find Full Text PDFGenetics
July 1996
Department of Genetics, University of Nottingham, Queens Medical Centre, United Kingdom.
Analysis of the aroLM-sbcCD interval of the Escherichia coli K-12 chromosome revealed a new gene (rdgC) encoding a function required for growth in recombination-deficient recBC sbcBC strains. Deletion of rdgC does not reduce viability, conjugational recombination, or DNA repair in rec+, recA, recB, recF, or recJ mutants. However, it makes the growth of recBC sbcBC strains reliant on the RecA, RecF, and RuvC proteins and, to a large extent, on RuvAB.
View Article and Find Full Text PDFAntimicrob Agents Chemother
August 1989
Department of Microbiology and Immunology, Medical College of Virginia/Virginia Commonwealth University, Richmond 23298.
Homologous genes encoding resistance to gentamicin, tobramycin, and kanamycin through the bifunctional acetylating [AAC(6')] and phosphorylating [APH(2")] aminoglycoside-modifying enzyme were identified in staphylococci isolated from patients in the United States. The mobility of gentamicin resistance (Gmr) genes found on a prototype conjugative plasmid (pGO1) was compared with that of genes cloned from chromosomal sites. Plasmid-encoded Gmr genes and flanking sequences were introduced onto a temperature-sensitive plasmid (pRN3208) from pGO1 by homologous recombination between insertion sequence-like elements present on both replicons.
View Article and Find Full Text PDFMol Microbiol
January 1989
Department of Microbiology, Iowa State University, Ames 50011.
As an alternative approach to genetic transfer and analysis, a novel integrable plasmid system was developed that should prove useful for mapping and cloning various genes in Staphylococcus aureus and other Gram-positive bacteria. The use of a restriction-deficient recipient strain and an improved protocol for protoplast plasmid transformation facilitated direct cloning of a recombinant plasmid (pPQ126) in S. aureus NCTC 8325-4.
View Article and Find Full Text PDFBroad host range IncP-1 plasmids are able to integrate into the chromosome of gram-negative bacteria. Strains carrying an integrated plasmid can be obtained when the markers of a temperature-sensitive (ts) plasmid derivative are selected at non-permissive temperature; in this way Hfr (high frequency) donor strains can be formed. The integrated plasmids, however, tend to be unstable in the absence of continuous selective pressure.
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