Abstract
The a sequence of herpes simplex virus (HSV) is present as a direct repeat at the genomic termini and also in inverted orientation at the joint between the L [long] and S [short] segments. DNA sequences were determined for the joint regions of the genomes of HSV-1 and HSV-2, and relative to these sequences the genomic termini are, in both cases, located close to a short direct repeat of 17-21 base pairs (bp) at the b-a and a-c junctions. The HSV-1 joint region contains 3 separate tandem direct reiterations of short sequences, (12, 16 and 17 bp in strain 17) and size heterogeneity in the a and c sequences is apparently due to variable copy numbers of these repeated units. A considerable part of the HSV-1 joint region probably does not code for polypeptide.