Organization within the mammalian kinetochore.
The organization within the mammalian kinetochore was examined using whole-mount electron microscopic techniques on chromosomes digested with restriction enzymes or micrococcal nuclease. These preparations revealed that a portion of the kinetochore is highly resistant to nuclease digestion and can be visualized as a discrete structure. The relationship of this structure to the remainder of the chromosome suggests that it represents the outer kinetochore plate. The plate is composed of a series of fibrillar loops that are arranged in a parallel array along the plane of the plate. These fibers are 25-30 nm in diameter. The morphology, particulate substructure, and ultimate susceptibility to nuclease digestion suggest that these fibers contain DNA. A model is presented that suggests that the outer plate contains the apexes of chromatin loops that originate within the body of the primary constriction.
D000818:Animals; D002478:Cells, Cultured; D002503:Centromere / Q000648:ultrastructure*; D002875:Chromosomes / Q000648:ultrastructure*; D003670:Deer; D007739:L Cells / Q000648:ultrastructure; D051379:Mice; D008854:Microscopy, Electron