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Brief Communication

Nature Genetics 39, 966–968 (1 August 2007) | doi:10.1038/ng2065

Bi-orientation of achiasmatic chromosomes in meiosis I oocytes contributes to aneuploidy in mice

Anna Kouznetsova , Lisa Lister , Magnus Nordenskj|[ouml]|ld , Mary Herbert & Christer H|[ouml]||[ouml]|g

The spindle assembly checkpoint guards against chromosomal missegregation but does not induce arrest in oocytes that contain a few achiasmatic chromosomes (univalents). We followed the fate of univalents in oocytes during the first meiotic division, and although these preserved a meiotic kinetochore structure, they were also bi-oriented in a mitotic manner.