Figure 1.

Schematic of the location of the fifteen homing endonuclease genes indicated on a genomic map of bacteriophage T4. For simplicity, each genomic segment is drawn with the endonuclease in the same orientation, with relevant regulatory elements indicated. The GIY-YIG endonucleases are shown in yellow, while the HNH-type endonucleases are green. The hybrid endonuclease segF is drawn with both colours. The bacteriophage Aeh1 mobE endonuclease, which is not part of the bacteriophage T4 genome, is set in a box. An asterix (*) marks a predicted late promoter upstream of SegB.