Figure legend

Figure 5. Summary composite of the inferred sequence of morphological changes the centrosome undergoes during duplication, separation, and folding. Progression of time is indicated by large open arrows. For all stages only one section of a section series is shown. (a) Interphase; (b) early prophase; (c) midprophase; (d) late prophase; (e) early prometaphase; (f) prometaphase; (g) metaphase; (h, i, and k) various stages of telophase. Arrowheads indicate microtubules; small arrows indicate remnants of nuclear envelope. Scale bar = 0.5 um

Figure notes

The interphase centrosome comprises a multilayered core surrounded by an amorphous matrix, the corona, from which microtubules emanate to the cell periphery. In early prophase the centrosome increases in size. At the transition from prophase to prometaphase, the corona, in which g-tubulin is present, dissociates from the core, resulting in loss of cytoplasmic microtubules. The two outer layers splay apart, and g-tubulin reassociates with these layers at their inner surfaces to form new nucleation sites for spindle microtubules. Beginning in metaphase and throughout anaphase, the centrosome starts to curl and finally folds in telophase, resulting in the reformation of the interphase centrosome.