Question

Which of the following contain the 9 + 2 arrangement of microtubules, consisting of nine doublets of microtubules surrounding a pair of single microtubules?

A) both motile cilia and primary (nonmotile) cilia
B) centrioles only
C) both flagella and motile cilia
D) both basal bodies and primary (nonmotile) cilia
E) both centrioles and basal bodies

Answer 1

The structures that contain the 9 + 2 arrangement of microtubules are both flagella and motile cilia. This structural feature is essential for their roles in cell movement and locomotion, but is not present in primary cilia, centrioles, or basal bodies.

Step-by-step explanation:

The correct answer to which structures contain the 9 + 2 arrangement of microtubules is C) both flagella and motile cilia. The 9 + 2 structure refers to nine doublets of microtubules surrounding a pair of single microtubules. Both flagella and motile cilia share this structural feature, which is crucial for their function in locomotion.

It is important to note that the primary (nonmotile) cilia do not typically have the 9 + 2 arrangement. Instead, they often have a 9 + 0 structure, lacking the central pair of microtubules. Centrioles and basal bodies do contribute to the formation of cilia and flagella but they themselves do not contain the 9 + 2 arrangement as they have nine triplets of microtubules with no central microtubules.