Q.Describe the ultrastructure of a cilium or flagellum, including the arrangement of microtubules within the axoneme and the structure from which it develops.

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The axoneme shows a '9+2' microtubule arrangement (9 peripheral doublets + 2 central singlets), developing from the basal body. …

A cilium or flagellum is built around a core structure called the axoneme, itself covered by an extension of the cell's own plasma membrane. The axoneme shows the characteristic "9 + 2" arrangement of microtubules: nine pairs (doublets) of microtubules are arranged evenly around its circumference, enclosing a single further pair of individual (singlet) microtubules at the very centre -- the central pair. The peripheral doublets are linked to each other and to the central pair by radial spokes and dynein arms, whose coordinated, ATP-powered sliding action produces the bending movement of the cilium or flagellum. At its base, the axoneme develops from a short cylindrical structure called the ba …

Describe the axoneme's 9+2 microtubule layout first, then name the basal body as the structure it develops from …

Describing the basal body itself as having a '9+2' arrangement -- the basal body has a '9+0' pattern; only th …