Fractionation mutagenesis and similar consequences of mechanisms removing dispensable or less-expressed DNA in plants

► Plant gene loss is deletion by recombination-type mechanisms. ► After tetraploidy one gene of a pair tends to be lost because it is underexpressed. ► We propose an epigenetic model to solve simultaneously heterosis, genome dominance and biased fractionation. ► Announcing fractionation mutagenesis: nature's promoter bashing.