Therefore, it would seem plausible to assume that in polyploid wheats
the time, degree and the phase of condensation and decondensation at the
telophase of the last premeiotic mitosis determine the regular association,
in pairs, of homologues instead of homeologues. And that this phasing and
degree of condensation, also reflected during meiosis, is controlled by
chromosomes 5B and 6A. It may be that the genetic systems of chromosomes
5B and 6A ensure regular pairing among the homologues by controlling the
degree and phase of condensation and decondensation at the last premeiotic
telophase to bring about a point-by-point pairing of homologues only. This
then leads to pairing exclusively among homologues. However, this balanced
mechanism of 5B and 6A does not completely prevent the homeologues from
approximating each other leading to secondary associations, as was demonstrated
by KEMPANNA and RILEY (Heredity 19, 1964).
(Received January 16, 1968)
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