Which of the following is true about the structure of the microtubule wall?

A) ?-?-tubulin heterodimers are arranged with mixed orientation in each protofilament, and protofilaments are arranged with mixed polarity in the microtubule wall.
B) ?-?-tubulin heterodimers are arranged with the same orientation in each protofilament, and protofilaments are arranged with mixed polarity in the microtubule wall.
C) ?-?-tubulin heterodimers are arranged with the mixed orientation in each protofilament, and protofilaments are arranged with same polarity in the microtubule wall.
D) ?-?-tubulin heterodimers are arranged with the same orientation in each protofilament, and protofilaments are arranged with same polarity in the microtubule wall.
E) Orientation of the ?-?-tubulin heterodimers is completely random and depends on which end of the dimer first hits the end of the microtubule when it assembles.


Answer: D

Biology & Microbiology

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