Fig. 5.

Schematic representation of the possible origin of aberrant Het′ and Het + Del chromosomes in the 14- and 15-chromosome apomictic Boechera accessions. We assume asynapsis as a possible switch to modify chromatin and epigenetic status of a chromosome region. This region is then involved in a stepwise chromosome degeneration and heterochromatinization, leading ultimately to the Het chromosome. The Del chromosome is considered a translocation or recombinant chromosome between a B. stricta and B. holboellii chromosome.