Practice question

Centrioles are cylindrical non-membranous organelles formed of nine triplet microtubule blades arranged radially around central symmetry, each triplet composed of A, B, C complete and partial tubules, approximate dimensions 200 nanometer diameter and 500 nanometer length, embedded in pericentriolar material comprising pericentrin, CEP192, and gamma-tubulin ring complexes that nucleate microtubule asters. Duplication begins at G1 to S transition via master kinase PLK4 recruitment to mother centriole, SAS-6 cartwheel assembly providing nine-fold symmetry template, STIL and CPAP elongating procentriole in orthogonal orientation. During late G2 and early mitosis, centrosomes separate driven by kinesin-5 Eg5 and dynein, forming bipolar spindle poles that nucleate dynamic microtubules capturing kinetochores via Ndc80 complex attachment, ensuring accurate segregation of sister chromatids to daughter cells preventing aneuploidy and chromosomal instability. In interphase, mother centriole templates basal body anchoring primary cilium axoneme containing 9+0 microtubules for Hedgehog signaling and motile cilia 9+2 for mucus clearance. They do not produce proteins, lipids, or ATP; synthesis belongs to ribosomes, ER, and mitochondria respectively.