Figure 10

Hypothetical model illustrating a cascade of events accompanying 5S rDNA evolution in Asteraceae. (A) Mobilisation of 5S genes by a retrotransposition event and their integration within the 35S unit; (B) short (< 100 units) tandems of 35S-5S repeats generated by intralocus non-homologous recombination; inactivation of retroelement activity by mutation and/or epigenetic silencing. (C) amplification and spreading of 35S-5S arrays across the chromosomes mediated by mechanisms such rolling circle replication and reintegration of covalently linked circles. Loss of arrays of unlinked units. Green rectangles - units of 35S genes, red rectangles - units of 5S genes. Dotted line depicts the reversion process from linked to unlinked genotype. For the simplicity, proportions of gene sizes are not in scale.