Recombination of transfected DNAs in vertebrate cells in culture

We studied the frequency of homologous and illegitimate recombinations between transfected noninfectious retroviral DNA molecules in chicken embryo fibroblasts. The frequency of recombination was determined by the formation of infectious virus and varied with the extent of homology between the DNA molecules at the site of recombination, but only when there were regions of homology surrounding this region. While homologous recombination led to the formation of wild-type virus, illegitimate recombination resulted in formation of infectious virus with alterations at the site of recombination. Apparent homologous recombination was also observed between transfected and chromosomal DNAs in D17 dog cells.