= Kinetochore ablation experiment
In 1995, <Conly L. Rieder>, <Richard W. Cole>, <Alexey Khodjakov> and <Greenfield Sluder> tested whether an unattached <kinetochore> supplies the inhibitory signal delaying <anaphase>. Living PtK1 <biological cells> on glass coverslips were mounted in Rose chambers at $35$–$37\,{}^\circ\mathrm{C}$. An inverted microscope with a $60\times$ objective recorded <differential interference contrast microscopy> video. A pulsed $532\,\mathrm{nm}$ <laser> focused through that objective destroyed selected <chromosome> regions. The readout was <chromosome> movement and <anaphase> onset before and after surgery.<The checkpoint delaying anaphase in response to chromosome monoorientation is mediated by an inhibitory signal produced by unattached kinetochores by Conly L. Rieder and others>[pp. 941–942, Abstract and Materials and Methods: Cell Culture; Laser Microsurgery and Video-enhanced Light Microscopy]{ref}
Destroying the last unattached <kinetochore> permitted <anaphase> without that <chromosome> aligning. Cutting <chromosome> arms served as a damage control: progression still awaited attachment of the last naturally one-pole-attached <chromosome>. Correlative <electron microscopy> checked the absence of the targeted <kinetochore>. Together these results located an inhibitory activity in or near the unattached <kinetochore>, rather than establishing a requirement for alignment itself.<The checkpoint delaying anaphase in response to chromosome monoorientation is mediated by an inhibitory signal produced by unattached kinetochores by Conly L. Rieder and others>[pp. 943–947, arm-cutting control, Table I, Figures 1, 5 and 6; destruction of the last unattached kinetochore and correlative electron microscopy]{ref}
This intervention localized control; it did not identify every signaling <molecule> or guarantee faithful inheritance after damage. The cultured PtK1 preparation differs from the hypothetical $2n=4$ cartoon. Neither the cartoon nor this experiment establishes identical control in every <species>.
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