Competitive Centromeres

摘要

A case of strongly distorted genetic ratios in hybrids between two species of the monkeyflower Mimulus seems to be due to a competitive advantage of one version of a chromosome over its partner's homologous region during female gamete formation. On page 1559 of this issue, Fishman and Saunders (1) provide cytoge-netic and genetic evidence implicating the centromere region of this chromosome. In most eukaryotes, segregation of chromosomes during cell division is controlled by the centromere regions. The new study suggests that the more competitive type of centromere spread recently in one of the species, M. guttatus, but not throughout the whole species, as one might have expected from its strong advantage. There may thus be some counterbalancing disadvantage. This system may advance our understanding of centromere behavior.