Schematic diagram of the sequence arrangement of the HSV-1 genome showing the location of the UL13 and α0 genes. Line 1 is a linear representation of the HSV-1(F) genome. The thin lines represent the unique long (UL) and unique short (US) sequences. The terminal repeats flanking the unique sequences are shown as open rectangles. Line 2 is an expanded section of the coding domain of the UL13 gene. The transcript is represented by a line capped by an arrowhead, and the coding domain of UL13 is represented by an open rectangle. R7356 contains a deletion spanning HindIII to BstEII restriction endonuclease sites within the UL13 coding domain. Line 3 is an expanded section of the coding domain of the α0 gene. The transcript and coding regions are shown for only one copy of the α0 gene. A second, identical copy is located in the terminal inverted repeat flanking UL. R7910 contains deletions of the entire coding regions of α0 genes spanning AseI to NotI sites. Bs, BstEII; H, HindIII; No, NotI; As, AseI.