Figure 4.

Trans-chromosomal methylation and demethylation. Four hypothetical loci (A–D) that are differentially methylated between two varieties. At loci A and C, there is no allelic interaction, and methylation depends on the genetic background (green is methylated, purple is unmethylated). At locus B, TCM triggers methylation on the previously unmethylated allele (orange hexagon). In repeated backcrosses to the unmethylated background, the newly methylated allele continues to induce methylation of naive alleles. At locus D, TCdM results in demethylation of the high methylation alleles (grey dashed hexagon). This unmethylated state continues to cause TCdM in subsequent generations of backcrossing to the methylated allele.