<P> The two centrioles in the centrosome are tied to one another . The mother centriole has radiating appendages at the distal end of its long axis and is attached to its daughter at the proximal end . Each daughter cell formed after cell division will inherit one of these pairs . Centrioles start duplicating when DNA replicates . </P> <P> The last common ancestor of all eukaryotes was a ciliated cell with centrioles . Some lineages of eukaryotes, such as land plants, do not have centrioles except in their motile male gametes . Centrioles are completely absent from all cells of conifers and flowering plants, which do not have ciliate or flagellate gametes . It is unclear if the last common ancestor had one or two cilia . Important genes required for centriole growth, like centrins, are only found in eukaryotes and not in bacteria or archaeans . </P> <P> The word centriole (/ ˈsɛntrioʊl /) uses combining forms of centri - and - ole, yielding "little central part", which describes a centriole's typical location near the center of the cell . </P> <P> Typical centrioles are made of 9 triplets of microtubules organized with radial symmetry . Centrioles can vary the number of microtubules and can be made of 9 doublets of microtubules (as in Drosophila melanogaster) or 9 singlets microtubules as in C. elegans . Atypical centrioles are centrioles that do not have microtubules such as the Proximal Centriole - Like found in Drosophila melanogaster sperm . </P>

Where is a centriole located in a cell