Unstable heterozygosity in a diploid region of herpes simplex virus DNA

We have examined the behavior of a herpes simplex virus strain KOS isolate in which the two inverted repeats flanking the short segment of viral DNA differ in length by approximately 60 base pairs. We find that individual viral DNA molecules exist which contain the two distinguishable repeats, demonstrating that heterology between the repeats is tolerated. However, viruses heterozygous for the two different repeats are unstable, segregating both classes of homozygotes at a high frequency. We propose that this segregation is a consequence of the high-frequency recombination events which also result in genome segment inversion.