Physical breakage of
the DNA molecule in two
non-homologous chromosomes can produce "sticky ends" that recombine end-to-end (top
right). The ends of the chromosomes are lost as acentric fragments. In a
standard metaphase chromosome
spread, the replicated chromosomes appear as a single chromosome
with two centromeres.
At mitosis or meiosis, the two centromeres may segregate together
to the same pole so as to produce a product a more or
less complete gene set. Alternatively, they may segregate to
alternate poles, in which case the region between the two
centromeres will be broken at random, and produce segmental
aneuploidy in the daughter cells.