Problem:

Question 1: Why do you think that some cells like neurons and muscle cells remain permanently in G0 after we reach adulthood? Explain.

Question 2: Mitotic spindle microtubules are polar structures in that one end (called the "+" end) polymerizes and depolymerizes (builds up and breaks down) at a much higher rate than the other end (the "-" end). Which end do you think is the "+" and which is the "-"? What evidence from mitosis provides evidence for your answer? Note, the "+" and "-" in this case has nothing to do with chemical charges!

Question 3: Many chemotherapy drugs used to treat cancer work by modifying the mitotic spindle. Paclitaxel works by interfering with normal microtubule breakdown during cell division and Vinblastine works by binding tubulin, thereby inhibiting the assembly of microtubules. How specifically do you think these drugs would stop a cancer cell? What consequences might taking these drugs have for a cancer patient?

Question 4: Many species can reproduce asexually and sexually. What kind of environment do you think would favor asexual reproduction or sexual reproduction? Speculate about the evolutionary significance of this switch from asexual to sexual reproduction.

Please read all the questions carefully and answer them.