Question

Which of the following statements is incorrect for centrioles?
A. Both the centrioles in a centrosome lie perpendicular to each other.
B. Central proteinaceous hub is missing in a centriole.
C. Each centriole has an organization like that of a cartwheel.
D. Centrosome usually contains 2 cylindrical centrioles.

Answer 1

Hint: The centriole is present in most of the eukaryotic cells which have a cylindrical structure and is made up of tubulin protein. It plays a role in the production of cilia during the interphase stage and the aster and spindle formation during the cell division.

Complete answer:
The centriole is an organelle having a cylindrical structure. It is present in most of the eukaryotic cells in the form of pairs surrounded by a pericentriolar material, thus forming a structure called the centrosome. In the centrosome, two centrioles lie perpendicular to each other in which each of the centrioles has an organization like that of a cartwheel. A centriole is made up of 9 evenly spaced microtubules that are made up of tubulin protein. Also, the central part of the proximal region of the centriole is a proteinaceous hub that is connected with the triplets on the peripheral side by radial spokes.
Options (A), (C), and (D) are incorrect because these three options are correct for centrioles.
Option (B) is correct because the statement- central proteinaceous hub is missing in a centriole is incorrect for centriole.

Hence, the correct option is (B).

Additional information:
The centriole is located inside the cytoplasm near the nuclear envelope. The main function of centriole is to facilitate the separation of the chromosomes that help in cell division. It can be found in animal cells, lower plants, and at the base of cilia and flagella.

Note:
Centriole possesses a 9+2 arrangement of microtubules that gives an appearance like that of a cartwheel in which a central proteinaceous hub (2 unfused microtubules) is connected to the 9 fused microtubules present at the periphery of the cylinder through radial spokes.