The arrangements of microtubules in centriole is
A) 9+2
B) 2+9
C) 11+0
D) 9+3

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Hint:Let us first understand what is meant by centriole. Centriole is a cell organelle that consists of a small set of microtubules that are arranged in a particular fashion and are found in most of the eukaryotes. It mainly consists of a protein known as tubulin.

Complete answer:
 Centriole is made up of nine triplets of microtubules that are arranged in a circular way. The two adjacent centrioles are usually at right angles to each other. This arrangement of a ring of nine microtubules is called triplets. These microtubules are attached to two other partial microtubules. The important function of centrioles is to produce spindle and aster during cell division and to produce cilia during interphase.

Additional information: The pair of centrioles is covered with a mass of dense material known as Pericentriolar material (PCM) that forms a structure called centrosome. During cell division, the centriole produces the spindle fibres that helps in the separation of the chromosomes. This process occurs during the anaphase of mitosis. In this stage the chromosomes are pulled by the spindle fibres towards opposite poles of the cell. The chromosomes cannot move without the presence of centrioles.

Therefore the correct answer is option (A) 9+2 .

Note: Centrioles are not present in angiosperms and fungi. They are present only in male gametes bryophytes, cycads, charophytes etc. The position of the nucleus is determined by the position of the centriole. In spatial arrangement of the cell, centriole plays a vital role.