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Chromosome pairing configuration. (A) Pollen mother cells (PMCs) of tetraploid ‘Mexican’ lime. (B) Schematic interpretation of (A) one univalent (blue) + 12 bivalents (black) + one trivalent (green) + two tetravalents (red). (C) Open tetravalent (arrow). (D–F) Closed (ring) tetravalents (arrows).
