FIGURE 18-9 Dynamic instability of microtubules in vitro. Individual microtubules can be observed in the light microscope and their lengths plotted at different times during assembly and disassembly. Assembly and disassembly each proceed at uniform rates, but there is a big difference between the rate of assembly and that of disassembly, as seen in the different slopes of the lines. Shortening of a microtubule is much more rapid (7 µm/min) than growth (1 µm/min). Notice the abrupt transitions to the shrinkage stage (catastrophe) and to the elongation stage (rescue).

[Data from P. M. Bayley, K. K. Sharma, and S. R. Martin, 1994, in Microtubules, Wiley-Liss, p. 118.]