Which of the following events is due directly to APC activit

Which of the following events is due directly to APC activity and is not an indirect consequence of inactivating MPF?

A. Increased MT stability.

B. Sister chromatid separation.

C. Nuclear envelope reformation.

D. Chromosome decondensation.

E. Formation of a contractile ring.

Solution

Sister chromatid separation occurs at the anaphase at which point the maturation promotion factor is disassembled as a result of marking by the anaphase promoting complex. This shows that option (b) Sister chromatid separation, is as a result of the APC and inactivation of MPF.

Activating the maturation promotion factor (MPF) leads to the stabilization of the microtubule involved in the mitotic spindle thus leading to its denaturation. This prevents the cell cycle to move on from the G2 to the M phase. This shows that option (a) Increased MT stability, is not the right choice.

Nuclear envelope degradation is associated with the activation of MPF. MPF acts on lamins by reducing the stability of the nuclear membrane, thereby degrading it. This shows that option (c) Nuclear envelope reformation, is not an activity of APC and an indirect activity as a result of MPF deactivation, and hence, not the right option.

Chromosomal decondensation is an activity that is formed by the activation of MPF. This shows that option (d) Chromosome decondensation, is not an activity of APC and an indirect activity as a result of MPF deactivation, and hence, not the right option.

Reformation of the contractile ring is preceded by the formation of nuclear membrane or nuclear envelope. Active MPF leads to the degradation of the nuclear membrane, so inactivation of the MPF should lead to the formation of nuclear membrane. It is only after the reformation of nuclear membrane, the contractile ring would be formed. This shows that option (e) Formation of contractile ring, is not an activity of APC and an indirect activity as a result of MPF deactivation, and hence, not the right option.