A meiotic mystery: How sister kinetochores avoid being pulled in opposite directions during the first division

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Abstract

We now take for granted that despite the disproportionate contribution of females to initial growth of their progeny, there is little or no asymmetry in the contribution of males and females to the eventual character of their shared offspring. In fact, this key insight was only established towards the end of the eighteenth century by Joseph Koelreuter's pioneering plant breeding experiments. If males and females supply equal amounts of hereditary material, then the latter must double each time an embryo is conceived. How then does the amount of this mysterious stuff not multiply exponentially from generation to generation? A compensatory mechanism for diluting the hereditary material must exist, one that ensures that if each parent contributes one half, each grandparent contributes a quarter, and each great grandparent merely an eighth. An important piece of the puzzle of how hereditary material is diluted at each generation has been elucidated over the past ten years.

Sister kinetochores are pulled in opposite directions by microtubules during mitosis. During meiosis I, they co-orient and maternal and paternal kinetochore pairs are instead pulled in opposite directions. In S. cerevisiae, monopolin confers co-orientation by interacting with kinetochore proteins but in S. pombe, cohesin holding sister centromeres together has been implicated.

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