The microtubule-binding protein Patronin binds to the minus ends of microtubules at the spindle pole and protects them from the effect of catastrophe factors. If Patronin activity is inhibited by injecting an anti-Patronin antibody into Drosophila melanogaster embryos prior to cellularization, anaphase B is suppressed and the spindles are significantly shorter. Which of the forces (1 or 2) in the following schematic diagram do you think is mostly responsible for anaphase B in this organism at this stage? Does the effect of Patronin inhibition resemble that of kinesin-5 inhibition (I) or overactivation (O)?
A) 1; I
B) 1; O
C) 2; I
D) 2; O

Question

The microtubule-binding protein Patronin binds to the minus ends of microtubules at the spindle pole and protects them from the effect of catastrophe factors. If Patronin activity is inhibited by injecting an anti-Patronin antibody into Drosophila melanogaster embryos prior to cellularization, anaphase B is suppressed and the spindles are significantly shorter. Which of the forces (1 or 2) in the following schematic diagram do you think is mostly responsible for anaphase B in this organism at this stage? Does the effect of Patronin inhibition resemble that of kinesin-5 inhibition (I) or overactivation (O)? 
A) 1; I 
B) 1; O 
C) 2; I 
D) 2; O

Quizplus · Accepted Answer

The force generated by kinesin-5 to lengthen the spindle in anaphase B is counteracted by catastrophe factors at the poles, which are inhibited by Patronin. Inhibition of Patronin would therefore result in anaphase B suppression.

The Microtubule-Binding Protein Patronin Binds to the Minus Ends of Microtubules