Question

• Describe in detail the roles of the three types of microtubules (kinetichore, astral & polar) associated with the spindle apparatus during mitosis – (1.5 pts.)

• Describe the roles of kinesins and dyneins in aligning the chromosomes during mitosis (0.5 pts.)

Answer 1

Microtubules	roles during mitosis
1.Kinetochore figure:kinetochore struccture	During mitosis,chromosomes condense and two copies visible as sister chromatids.one kinetochore is assembled on each of the two sister chromatids of chromasome,and both sister kinetochore become attached to two opposite spidle poles.
2.Astralfigure:shows three microtubles,astral,kinetochore,and polar	They are microtubules radiated from centrosphere. They help position the mitotic apparatus and also help to determine the clevage plane during cytokinase.
3.polar	polar microtubules oriented parallel to each other but in opposing direction,are crucial for pushing the spindle apparatus during mitosis

ROLE OF KINESINS AND DYNEINS DURING MITOSIS

Microtubules act as tracks two classes of motor proteins

1.KINESINS

2.DYNEINS

1.KINESINS

• Move cargo to plus end
• During mitosis,participate in mitotic spindle dynamics
• Usually dimers of 2 heavy and 2 light chains figure:two classes of motor protein,kinesins and dyneins alliagnment.

2.DYNEINS

• Move cargo to the minus end
• During mitosis participate in mitotic spidle dynamics
• power beating cilia and flagella
• Large protein complex with many subunit