Question

Which of the following is the correct answer regarding the structure of a section of cilia/flagella?

\[ \begin{array}{|c|c|c|c|c|} \hline & \begin{array}{c} \text{Peripheral microtubules} \\ \text{(doublets)} \end{array} & \begin{array}{c} \text{Central microtubules} \\ \text{(singlets)} \end{array} & \text{Radial spokes} & \text{Central sheath} \\ \hline A & 9+0 & 2 & 8 & 1 \\ \hline B & 9+2 & 9+0 & 9 & 2 \\ \hline C & 9 & 2 & 9 & 1 \\ \hline D & 3 & 6 & 9 & 1 \\ \hline \end{array} \]

• A. A
• B. B
• C. C
• D. D

Hint:

Structure of eukaryotic cilia/flagella: \[ \boxed{ 9\ \text{peripheral doublets} +2\ \text{central singlets} } \] with 9 radial spokes and one central sheath.

Answer 1

The Correct Option is C

Step 1: Recall the ultrastructure of cilia and flagella. A typical eukaryotic cilium/flagellum has the \[ \boxed{9+2} \] arrangement consisting of - 9 peripheral microtubule doublets, - 2 central singlet microtubules, - 9 radial spokes, - 1 central sheath.

Step 2: Compare with the options. \[ \boxed{ \begin{aligned} \text{Peripheral doublets} &=9 \text{Central singlets} &=2 \text{Radial spokes} &=9 \text{Central sheath} &=1 \end{aligned} } \] This corresponds to option (C).

Step 3: Choose the correct option. Therefore, \[ \boxed{(C)} \] is the correct answer.