Practice question

Kinetochore-microtubule interactions evolve through search and capture mechanism mediated by dynamic microtubule instability. Successful biorientation defined as amphitelic configuration where sister kinetochores attached to microtubules originating from opposite spindle poles. This arrangement produces pulling forces toward poles resisted by centromeric cohesin complex linking sisters, generating inter-kinetochore tension about 0.5 to 1 micron stretch detectable as separation between CENP-A foci. Tension acts as stabilization signal and silences spindle checkpoint. By contrast monotelic state where single sister attached leaves other unattached signaling MCC production, syntelic where both sisters attach same pole lacks inter-sister tension causing Aurora B dependent destabilization, and merotelic where single kinetochore captures microtubules from both poles creates lagging chromosome because tension partly satisfied but attachment merotelically bridging both poles; if uncorrected leads to aneuploidy. Merotelic errors particularly common and require Aurora B and MCAK for resolution. Achievement of amphitelic attachment for all chromosomes manifests as congression to equatorial metaphase plate, fulfilling condition for APC/C-Cdc20 activation and securin degradation. Additional feedback loops involving polo-like kinases, phosphatases and SCF-mediated degradation reinforce irreversibility and protect against premature progression that would compromise genome integrity and viability.