The asymmetry of female meiosis reduces the frequency of inheritance of unpaired chromosomes

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Abstract

Trisomy, the presence of a third copy of one chromosome, is deleterious and results in inviable or defective progeny if passed through the germ line. Random segregation of an extra chromosome is predicted to result in a high frequency of trisomic offspring from a trisomic parent. C. elegans with trisomy of the X chromosome, however, have far fewer trisomic offspring than expected. We found that the extra X chromosome was preferentially eliminated during anaphase I of female meiosis. We utilized a mutant with a specific defect in pairing of the X chromosome as a model to investigate the apparent bias against univalent inheritance. First, univalents lagged during anaphase I and their movement was biased toward the cortex and future polar body. Second, late-lagging univalents were frequently captured by the ingressing polar body contractile ring. The asymmetry of female meiosis can thus partially correct pre-existing trisomy.

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Daniel B Cortes

Department of Molecular and Cellular Biology, University of California, Davis, Davis, United States

Competing interests
The authors declare that no competing interests exist.
Karen L McNally

Department of Molecular and Cellular Biology, University of California, Davis, Davis, United States

Competing interests
The authors declare that no competing interests exist.
Paul E Mains

Department of Biochemistry and Molecular Biology, University of Calgary, Calgary, Canada

Competing interests
The authors declare that no competing interests exist.
Francis J McNally

Department of Molecular and Cellular Biology, University of California, Davis, Davis, United States

For correspondence
fjmcnally@ucdavis.edu

Competing interests
The authors declare that no competing interests exist.

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