Sometimes, more is less: so in the case of some genes that become less active if there are more chromosomes. This attracted Ortrun’s attention when it occurred in Arabidopsis thaliana, a plant with usually 5 x 2 chromosomes (diploids), after genome duplication to 5 x 4 chromosomes (tetraploids). The unexpected loss of gene expression is heritable and can impinge on previously active copies after an encounter with inactive copies in tetraploid plants. The group in Vienna tries to find out how such changes are established and maintained and why two plus two does not always equal four.