Genome sizes are 5.4 kb, 5.6 kb, 6.4 kb, 4.2 kb, 4.3 kb, and 3.6 kb, respectively. Protein-coding regions represent between 91% (F1) and 96% (ΦX174) of the total genome, respectively. Arrows indicate the location of each cistron and colors represent broad functional categories (blue: replication; green: particle assembly; yellow: coat; red: lysis/extrusion; grey: other/unknown). However, several genes are multifunctional; for instance A2 is involved in phage assembly and lysis. The location of each of the mutations fixed in the mutation-accumulation lines is shown within white bars, each bar corresponding to an independent line (see for details). The three DNA phages have circular genomes but are shown in linear form for convenience. The genomes of ΦX174 and G4 are shown collinearly to indicate gene homology. However, by convention, the first position of the ΦX174 genome is assigned to the unique Pst I cleavage site (vertical dashed line).