title: Centromere ultrastructure in germ-line chromosomes of Parascaris.
abstract: Ultrastructural analysis of the centromere in germ-line mitotic chromosomes of Parascaris univalens and Parascaris equorum revealed that these chromosomes are holocentric. In thin longitudinal sections of both species the kinetochore appeared as a continuous plate (up to 3.8 micron long) and displayed a layered structure. This structure consisted of electron-dense inner and outer layers (average width 10 nm) separated by a less dense middle layer (25 nm wide), which had transverse electron-dense bars (10 nm wide) regularly spaced every 25-30 nm. Thus the ladderlike kinetochore profile observed in Parascaris gonial mitotic chromosomes represents a different type of organization from that of the classical trilaminar kinetochore found in both holocentric and monocentric chromosomes.
mesh_terms: D000818:Animals; D001199:Ascaridoidea / Q000648:ultrastructure*; D002503:Centromere / Q000648:ultrastructure*; D002875:Chromosomes / Q000648:ultrastructure*; D008854:Microscopy, Electron; D008938:Mitosis; D008941:Spindle Apparatus / Q000648:ultrastructure