Figure 1.

Centromere DNA sequences diverge rapidly and kinetochore components evolve adaptively. (a) Centromeres (white boxes) nucleate a specialized set of proteins called the kinetochore (blue), including CENP-A and CENP-C (green), which in turn interact with the spindle microtubules (red lines). As centromere sequences diverge, either CENP-A or CENP-C has evolved adaptively (darker green) in different lineages. (b) Changes in the sequence or organization of centromere DNA (yellow boxes) may create stronger centromeres (indicated, for convenience, by a greater number of microtubule interactions). Selective segregation of stronger centromeres into egg cells could, theoretically, lead to meiotic drive (see text for details). (c) Meiotic drive in female meioses could generate imbalances in subsequent male meioses. Such imbalances might in turn be neutralized by adaptive evolution (circular arrows) of kinetochore proteins such as CENP-A or CENP-C.