Cytogenetic effects of diethylstilbestrol (DES) Which cellular effect is most characteristically associated with DES exposure during cell division studies?

Introduction / Context:
Diethylstilbestrol (DES) is a synthetic estrogen historically used in medicine and later recognized for adverse developmental and carcinogenic effects. In cytogenetic assays, certain chemicals act as clastogens (causing chromosome breaks) or aneugens (interfering with the mitotic spindle and chromosome segregation). Distinguishing these mechanisms improves interpretation of micronucleus and karyotypic data.

Given Data / Assumptions:

• Focus is on mitotic effects observable in cell division studies.
• We compare spindle disruption versus isolated phenomena like centriole elongation.
• Endpoints such as lagging chromosomes can be downstream consequences of spindle defects.

Concept / Approach:
Aneugens alter the spindle apparatus or kinetochore function, promoting mis-segregation (nondisjunction, lagging chromatids). DES has been reported in several test systems to perturb microtubule dynamics and spindle function, consistent with aneugenicity. While chromosome lagging may be observed, it is typically a consequence of spindle interference rather than the fundamental, defining action itself.

Step-by-Step Solution:

Verification / Alternative check:
Micronucleus assays distinguishing kinetochore-positive micronuclei (aneugenic) from kinetochore-negative (clastogenic) support spindle interference when kinetochore-positive bodies increase after DES exposure in certain systems.

Why Other Options Are Wrong:

• Chromosome lagging only: a sign, not the root mechanism.
• Centriole elongation: not the primary, broadly reported cytogenetic effect of DES.
• All equally: overgeneralizes; evidence points most strongly to spindle interference.
• No effect: contradicted by numerous toxicology studies.

Common Pitfalls:
Equating any visible mitotic anomaly with the mechanism; always link the phenotype back to spindle or DNA damage pathways.

Final Answer:
Disruption of the mitotic spindle (aneugenic effect)