Becker's World of the Cell 9th Edition by Lewis Kleinsmith, Jeff Hardin, Gregory Paul Bertoni

Exercise 8

Tipped Off. Polarized cytoskeletal structures and intraflagellar transport (IFT)are involved in formation of cilia and flagella.
(a)Observation of flagella in the biflagellate alga, Chlamy- domonas reinhardtii, indicates that particles move toward the tips of flagella at a rate of 2.5 m/min., but the particles moving back toward the base of flagella move at 4 m/min. How do you explain this difference in rate of movement
(b)Temperature-sensitive mutations in a kinesin II required for intraflagellar transport (IFT)have been identified in Chlamydomonas. Such mutations only lead to defects when the temperature is raised above a certain threshold, called the restrictive temperature. When algae with fully formed flagella are grown at the restrictive temperature, their flagella degenerate. What can you conclude about the necessity of IFT from this experiment
(c)Based on your knowledge of the directionality of microtubule motors and the information in (b), where would you predict that the plus ends of flagellar microtubules are State your reasoning.