Question

The usual axonemal arrangement of microtubules is

• A. 6 pairs of doublets radially arranged at periphery with a pair of centrally located microtubules
• B. 6 pairs of doublets radially arranged at periphery with a single centrally located microtubule
• C. 9 pairs of doublets radially arranged at periphery with a pair of centrally located microtubules
• D. 9 pairs of doublets radially arranged at periphery with a single centrally located microtubule

Answer 1

Answer: (C)

The core of cilium or flagellum is called axoneme which possesses a number of microtubules running parallel to the long axis. The axoneme usually has nine pairs of doublets of radially arranged peripheral microtubules and a pair of centrally located microtubules. Such an arrangement of axonemal microtubules is referred to as the $9+2$ array.