Q58.Given below are two statements:
Statement I:
Flagella has 9 + 2 arrangement of microtubules.
Statement II:
Centriole has 9 + 0 arrangement of microtubules.
In the light of the above statements, choose the most appropriate answer from the options given below:
(1) Both Statement I and Statement II are correct
(2) Both Statement I and Statement II are incorrect
(3) Statement I is correct but Statement II is incorrect
(4) Statement I is incorrect but Statement II is correct
Both statements are correct, making option (1) the right choice.
Microtubule Arrangements
Flagella feature a 9+2 microtubule structure in their axoneme, with nine peripheral doublet microtubules encircling two central singlet microtubules, enabling motility in eukaryotic cells. Centrioles, by contrast, exhibit a 9+0 pattern, consisting of nine triplet microtubules arranged cylindrically without a central pair, serving as organizers for spindle fibers during cell division.
Option Analysis
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Option 1: Correct—Statement I matches flagellar axoneme structure, and Statement II aligns with centriole composition.
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Option 2: Incorrect—both descriptions are standard in cell biology textbooks and electron microscopy studies.
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Option 3: Incorrect—Statement II is accurate for centrioles, which lack central microtubules unlike motile cilia/flagella.
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Option 4: Incorrect—flagella definitively show 9+2, distinguishing them from basal bodies or centrioles.
Introduction to Flagella 9+2 Centriole 9+0 Arrangement
In cell biology, the flagella 9+2 centriole 9+0 arrangement refers to distinct microtubule organizations critical for cellular motility and division. Eukaryotic flagella use a 9+2 setup for whip-like movement, while centrioles rely on 9+0 for structural roles. This guide breaks down the statements, verifies accuracy, and explores exam-style options.
Flagella: The 9+2 Microtubule Structure
Flagella contain an axoneme with nine outer doublet microtubules surrounding two central singlets, forming the 9+2 arrangement. Dynein arms on doublets generate sliding for propulsion in organisms like sperm or protozoa. This motile core anchors to a basal body, akin to a centriole.
Centriole: The 9+0 Microtubule Pattern
Centrioles feature nine triplet microtubules in a cartwheel array, denoted as 9+0, with no central pair. Each triplet includes A, B, and C subfibers; they organize mitotic spindles and form basal bodies for flagella. Variations exist in some species, but 9+0 is canonical.
Evaluating the Statements
Statement I correctly describes flagella’s 9+2 arrangement. Statement II accurately captures centriole’s 9+0 setup. Both hold true, so option (1) is ideal for competitive exams testing ultrastructure knowledge.
Exam Options Breakdown
Biological Significance
These arrangements highlight microtubule diversity: 9+2 drives locomotion, 9+0 supports division. Mutations disrupt functions, linking to ciliopathies or cancer. For students, mastering flagella 9+2 centriole 9+0 arrangement aids NEET, CSIR prep.
