Inverted Repetitions in the Chromosome of Herpes Simplex Virus

Single DNA strands will sometimes fold back on themselves and form duplex regions by base pairing. This behavior is diagnostic of repeated, complementary nucleotide sequences in the strand, which are inverted with respect to one another. Examples of such inverted repetitions (ABC … C′B′A′) have been found by electron microscopy in DNA from bacterial plasmids (Sharp et al. 1973), bacteriophage Mu (Hsu and Davidson 1974), eukaryotic chromatin (Thomas et al. 1974) and two animal viruses, adenovirus (Garon et al. 1972; Wolfson and Dressier 1972) and adeno-associated virus (Koczot et al. 1973; Gerry et al. 1973).