A targeting event at the endogenous Gat locus, in which integration of sequence from the donor template vector has occurred instead of homologous repair. The inserted sequence includes a eyaGMR.HMS04515 dominant marker; since there is essentially no recombination on the fourth chromosome, this means that the Gateya chromosome can serve as a 4th chromosome balancer, as it is both recessive lethal (due to Gateya) and causes a dominant scorable phenotype (due to the eyaGMR.HMS04515 marker).