Comparison of Foldback Sequences of Herpes Simplex Virus Types 1 and 2 DNA

The DNAs of herpes simplex virus types I and 2 (HSV-r and HSV-2) were separately denatured and allowed to renature briefly. The intrastrand foldback structures that resulted from base pairing of inverted repeated sequences on otherwise single-stranded (ss) DNA were visualized in the electron microscope. The two genomes were found to contain similar size classes of small duplex stem DNA sequences. However, HSV-2 DNA appeared to possess an additional, larger size class of foldback structures not found on HSV-I DNA. Both HSV DNAs were found to contain stem-plus-loop structures; the larger stem-plus-loop structures of the two genomes had similar stem lengths but dissimilar loop lengths. Thus, a comparison of the genomes of HSV-I and HSV-2 showed that they possessed similar size classes of foldback sequences