A possible scenario of teleost GRB duplication conceptually corresponds to the case of the target gene OTP and its bystander genes TBCA and AP3B1 (Fig. 2A). In one case (left), the bystander gene (bg) disappears by neutral evolution. This scenario directly demonstrates that HCNEs within and beyond the bystander gene do not control that gene but the target gene. Other scenarios are variations on the theme—for instance, after breaking off one of the copies of a bystander gene (or a set of bystander genes) from the corresponding copy of the target gene (right), it can be the broken-off copy that disappears, together with the HCNEs that lost contact with the target gene.
