Escherichia coli strain 86, isolated from a piglet with diarrhea, carries plasmid-linked genes for resistance to tetracycline, streptomycin, and sulfonamides and for production of heat-labile and heat-stable enterotoxin. Results of (i) genetic experiments involving conjugal transfer and phage P1-mediated transduction and (ii) physical experiments involving electron microscopic examination of pl...

The utility of restriction endonucleases as a tool in molecular biology is in large part due to the high degree of specificity with which they cleave well-characterized DNA recognition sequences. The specificity of restriction endonucleases is not absolute, yet many commonly used assays of biological phenomena and contemporary molecular biology techniques rely on the premise that restriction en...

Single-strand annealing (SSA) is an important homologous recombination mechanism that repairs DNA double strand breaks (DSBs) occurring between closely spaced repeat sequences. During SSA, the DSB is acted upon by exonucleases to reveal complementary sequences that anneal and are then repaired through tail clipping, DNA synthesis, and ligation steps. In baker's yeast, the Msh DNA mismatch recog...

DNA with base pair mismatches was prepared by annealing mixtures of genetically marked DNA from bacteriophage lambda. This heteroduplex DNA was used to transfect bacteria under conditions minimizing recombination. Genetic analysis of the progeny phages indicates that: (i) Mismatch repair occurs, usually giving rise to a DNA molecule with one chain with the genotype arising from repair and one p...

BACKGROUND Homologous recombination in Escherichia coli creates patches (non-crossovers) or splices (half crossovers), each of which may have associated heteroduplex DNA. Heteroduplex patches have recombinant DNA in one strand of the duplex, with parental flanking markers. Which DNA strand is exchanged in heteroduplex patches reflects the molecular mechanism of recombination. Several models for...

We have established an in vitro reaction in which heteroduplex DNA formation is dependent on the concerted actions of recA and recBCD proteins, the major components of the recBCD pathway of genetic recombination in vivo. We find that heteroduplex DNA formation requires three distinct enzymatic functions: first, the helicase activity of recBCD enzyme initiates heteroduplex DNA formation by unwin...