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(i) Draw a well-labelled diagram of T.S. of centriole. (ii) Give the functions of centriole.

GeneralClass 12AllAnswered 27 Mar 2026
Answer

Answer:

(i) T.S. (Transverse Section) of Centriole [Diagram in PDF shows]:

  • 9 triplet fibrils arranged radially (9+0)
  • Each triplet: A, B, C tubules (A-tubule complete, B and C incomplete)
  • Central hub (proteinaceous mass)
  • 9 radial spokes (cartwheel structure)
  • C-A connectives linking triplets
  • Pericentriolar satellites (massules) surrounding centriole

(ii) Functions of Centrioles:

  1. Spindle Fiber Formation:
    • Organize mitotic spindle during cell division
    • Centrosomes (containing centriole pairs) are microtubule organizing centers (MTOCs)
  2. Basal Body Formation:
    • Give rise to basal bodies of cilia and flagella
    • Basal bodies anchor and control ciliary/flagellar movement
  3. Cell Polarity:
    • Establish cell polarity and spatial organization
  4. Centriole Duplication:
    • Each centriole duplicates once per cell cycle
    • Ensures proper chromosome segregation

Occurrence: Present in animal cells, lower plants (Chlamydomonas), some fungi; absent in most higher plant cells and prokaryotes.

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