Sterile hybrid with genome AB undergoes doubling of chromosome set to form fertile tetraploid with genome AABB. But since A and B is not homologous, synapsis cannot occur at prophase I, so there is no meiosis. So how does the chromosomes double? If through non-disjunction in mitosis, where did it occur? Did it occur in one cell only or all of the cells in the organism? Did non-disjunction occurs at gonad to produce AABB cell, then it undergo meiosis to form AB gametes, and then self fertilise with AB gamete to form AABB offspring?

  • $\begingroup$ Kindly elaborate in which step of this entire process you are indicating non-disjunction? it seems simply a DNA replication can cause chromosome doubling or polyploidy. . $\endgroup$ – Always Confused Sep 1 '19 at 12:12
  • $\begingroup$ @AlwaysConfused DNA replication occurs only at meiosis or mitosis right? So in this case, it occurs in mitosis? $\endgroup$ – user9803530 Sep 1 '19 at 13:48

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