Fig. (2) Evidence for the occurrence of cross-over events. The percentages of nucleotide identity to EGFP gene decreased from 37% (21bp-165bp variable region) to 20% (C289T substitution), then increased to 38% (456bp-651bp variable region) and to 100% (672bp-696bp variable region). The changes indicated that cross-over events occurred in three conserved regions: 166bp-288bp, 290bp-455bp, and 652bp-671bp.