Final answer:
E. Kinesin-5 on interpolar microtubules and dynein on astral microtubules. motor proteins are more directly involved in anaphase B
Step-by-step explanation:
During anaphase B of mitosis, the separation of spindle poles involves the movement of interpolar microtubules away from each other. Kinesin-5 is a motor protein that plays a crucial role in this process by sliding apart overlapping interpolar microtubules, contributing to spindle elongation.
In addition to the action of kinesin-5, dynein, a minus-end-directed motor protein, is involved in anaphase B. Dynein acts on astral microtubules, which extend towards the cell cortex. Dynein's activity results in the pulling of spindle poles toward the cell cortex, contributing to the separation of spindle poles and the overall elongation of the spindle during anaphase B.
Therefore, option E correctly identifies the motor proteins more directly involved in anaphase B: Kinesin-5 on interpolar microtubules and dynein on astral microtubules. The combined action of these motor proteins ensures the proper segregation of chromosomes and the completion of mitosis.