Since each daughter cell receives only one pair of centrioles after cell division, the daughter cells must duplicate existing centrioles prior to cell division. In most somatic cells, duplication of centrioles begins near the transition between the G1 and S phases of the cell cycle. This event is closely associated with the activation of the cyclin E-Cdk2 complex during the S phase of the cell cycle (see Fig. 3.11). This
FIGURE 2.56  Schematic structure of centrioles. In nondividing cells, centrioles are arranged in pairs in which one centriole is aligned at a right angle to the other. One centriole is also more mature (generated at least two cell cycles earlier) than the other centriole, which was generated in the previous cell cycle. The mature centriole is characterized by the presence of satellites and appendages. Centrioles are located in close proximity to the nucleus. The basic components of each centriole are microtubule triplets that form the cylindrical structure surrounding an internal lumen. The proximal part of the lumen is lined by -tubulin, which provides the template for nucleation and arrangement of the microtubule triplets. The distal part of each lumen contains the protein centrin. In some species, two protein bridges, the proximal and distal connecting fbers, connect each centriole in a pair. In some species, but not in humans, the proximal end of each centriole is attached to the nuclear envelope by a contractile protein known as the nucleus–basal body connector.
complex directly phosphorylates the nucleus-chaperoning protein nucleophosmin/B23, which is responsible for initiating the duplication of centrioles.
In most cells, duplication begins with the splitting of a centriole pair, followed by the appearance of a small mass of fibrillar and granular material at the proximal lateral end of each original centrioles. Because the existing pair of centrioles serves as a core for new organelle formation, this process of centriole duplication is referred as the centriolar pathway (see Fig. 2.53). The fbrous granules coalesce into dense spherical structures called deuterosomes, and they give rise to the procentriole (or bud), which gradually enlarges to form a right-angle appendage to the parent (see Fig. 2.53). Microtubules begin to develop in the mass of fibrous granules as it grows (usually during the S to late G2 phases of the cell cycle), appearing first as a ring of nine single tubules, then as doublets, and finally as triplets. As procentrioles  mature  during the S and G2 phases of the cell cycle, each  parent–daughter pair migrates around the nucleus. Before the onset of mitosis, centrioles with surrounding amorphous pericentriolar material position themselves on opposite sides of the nucleus and produce astral microtubules. In doing so, they define the poles between which the bipolar mitotic spindle develops.
The important difference between duplication of centrioles during mitosis and during ciliogenesis is the fact that during mitosis only one daughter centriole buds from the lateral side of parent organelle, whereas during ciliogenesis as many as ten centrioles may develop around parent  centriole.
Development of cilia on the cell surface requires the presence of basal bodies, structures derived from centrioles.