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. Author manuscript; available in PMC: 2011 Jun 1.
Published in final edited form as: Cell Biol Int. 2010 Dec;34(12):1239–1245. doi: 10.1042/CBI20100612

Figure 3.

Figure 3

Schematic representation of the centriole cycle during the cell cycle in mammalian cells. Centrosomes are shown as a hollow circle of fine lines enclosing the centrioles, which are represented by paired parallel lines as if in longitudinal section. Cell at 1 o’clock is a G1 daughter cell that has inherited a single centrosome with two centrioles. In many cell types, the centrioles remain in close proximity, whereas in others (e.g. HeLa), the original mother and daughter centrioles can be widely separate. The 2 o’clock cell is in late G1, and the centrioles have separated slightly and have lost their orthogonal arrangement. Centriole disorientation was once thought to signal the initiation of centriole duplication, but more recent work has revealed that the centrioles become disengaged from each other starting in late mitosis. The cell at 4 o’clock is in early S-phase, and centriole duplication is underway with the assembly of short procentrioles at the proximal ends of the mother centrioles. The procentrioles elongate throughout the rest of interphase, reaching their mature length in mitosis or the following G1. The 6 o’clock cell is in late S or early G2. The procentrioles have become longer. The 8 o’clock cell is in G2, and the mother–daughter centrioles pairs have started to separate as the centrosome is resolving itself into two sister centrosomes. With time, the sister centrosomes continue to separate around the nucleus as the cell cycle approaches mitosis. At mitosis (10 o’clock), the sister centrosomes organize the two poles of the spindle. Each centrosome contains a mother centriole and its daughter. The cell at 12 o’clock is in late telophase, as it is completing cleavage. Centriole duplication is said to be conservative because the procentriole is assembled from subunits in the cytoplasm, not from components of the mother centriole. Centriole distribution to sister centrosomes is said to be semiconservative because parental centrioles are distributed to both centrosomes. Diagram after Wheatley (1982), by permission of Elsevier and the author.