Many plants are polyploid, that is, they carry an n-fold excess, often two, of entire sets of chromosomes relative to their ancestors. Some species exhibit variation in chromosome number within populations. One such plant is Arabidopsis arenosa, a close relative of the model system plant A thaliana; however, it is not known how these plants can avoid missegregation after chromosome doubling. Yant et al. examined meiotic chromosomes in natural tetraploid (resulting from a single doubling of chromosome number) and diploid A. arenosa and observed that the number of chiasmata (a measure of recombination) was reduced in the polyploid individuals. Induced polyploids, however, showed cytological abnormalities and significantly reduced fertility, suggesting that diploid A. arenosa are not adapted for the polyploid condition and that polyploids are subject to selection that acts to maintain proper meiosis and gamete formation.
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