Question

1. explain the securin seperase story. include a labeled picture.

Explanation:

The securin-separase system regulates sister chromatid separation in cell division. Securin binds to separase, inhibiting its activity during metaphase. When the cell is ready to divide (anaphase onset), the anaphase-promoting complex (APC/C) ubiquitinates securin, targeting it for degradation by the proteasome. This releases active separase, which cleaves cohesin (the protein holding sister chromatids together), allowing chromatids to move to opposite poles.

Labeled diagram description:

• Metaphase: Sister chromatids (labeled) connected by cohesin; separase (enzyme shape) bound and inhibited by securin (small protein shape).
• Anaphase signal: APC/C (complex shape) tags securin with ubiquitin (small marker).
• Anaphase: Securin degraded; active separase cleaves cohesin; chromatids separate.

Answer:

The securin-separase system controls sister chromatid separation: securin inhibits separase until APC/C-mediated degradation releases active separase to cleave cohesin. A labeled diagram would show metaphase (securin-bound separase, cohesive chromatids) and anaphase (degraded securin, active separase, separated chromatids) with key components labeled.