Figure 18-2: T4 gene maps. The outer circle shows the approximate positions of characterized genes on the 169,903 bp DNA, drawn as a circle. The next three genome segments show three maps derived from determining distances of chromosomal ends from rI, rII and rIII respectively (278). Note that the relative length of the small rI molecules was 0.77, not 0.68 of the normal T4 chromosome. The next (full) circle indicates the positions of genes derived from genetic crosses (105). The innermost circle indicates the positions of heteroduplex loops after annealing of heat-denatured T2, T4 and T6 DNA (201).