Cross contamination of the genomes in human/hamster cell hybrids by multiple short recombination events

We have isolated sites of de novo rearrangements from interspecific cell hybrids. Of 147,000 clones screened from a human/hamster hybrid genomic library, 14 clones were found with homology to both human and hamster repetitive DNA sequences. Five of these clones contained recombination events involving less than 13 kb of DNA, three with human DNA recombined into a section of hamster DNA, and two with hamster DNA recombined into human DNA. None of the clones involving human LI sequences were found to be de novo transposition events, but simply short recombination or insertion events. Considering the apparent random nature of these events, they are likely to involve unique as well as repetitive sequences and also involve integration into the homologous as well as heterologous chromosome sets. These results suggest that the chromosome sets in somatic cell hybrids may be randomly contaminated with small DNA segments derived from either set of chromosomes.