Question

With pure tubulin in vitro, the initial lag in the rate of microtubule formation is because: _____

Answer 1

The initial lag in microtubule formation is due to the time required for tubulin dimers to nucleate and form a stable structure for elongation.

Step-by-step explanation:

The initial lag in the rate of microtubule formation with pure tubulin in vitro is due to the time it takes for tubulin dimers to nucleate and form a stable base for elongation. Microtubules assemble from dimers of α-tubulin and β-tubulin monomers which then add to a growing plus end (+end) of the microtubule, a process that is fueled by GTP hydrolysis. This initial lag phase represents the time required for enough subunits to come together to form a stable structure that can effectively elongate, akin to the critical nucleus size in crystallization.